GAO

United States General Accounting Office

Congressional Requesters

May 2000 TOXIC CHEMICALS

Long-Term

Coordinated Strategy

Needed to Measure

Exposures in Humans

GAO/HEHS-00-80

Page 1 GAO/HEHS-00-80 Environmental Health Data Needs

Contents

Letter 3

Appendixes Appendix I: Objectives, Scope, and Methodology 46

Appendix II: Reported Gaps in Human Exposure Data and

History of Federal Efforts 52

Appendix III: Survey of State Environmental Health Officials and

Results 62

Appendix IV: Comments From the Department of Health and

Human Services 68

Appendix V: Comments From the Environmental Protection

Agency 73

Appendix VI: Major Contributors to This Report 78

Tables Table 1: Extent to Which Human Exposure Data Are Collected for

Potentially Harmful Chemicals Through NHANES or

the NHEXAS Pilot Surveys 14

Table 2: Prevalence of Elevated Blood Lead Levels in Children

Ages 1 Through 5, by Selected Demographic

Characteristics

(NHANES, 1991 Through 1994) 18

Table 3: Examples of How State Officials Use Human Exposure

Data 23

Table 4: Examples of Reports Calling for Coordination in

Environmental Health 32

Table 5: Number of Chemicals and Time Frames for Select

Federal Efforts 55
Contents

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Abbreviations

ATSDR Agency for Toxic Substances and Disease Registry

CDC Centers for Disease Control and Prevention

DP-HANES Defined Population Health and Nutrition Examination Survey

EPA Environmental Protection Agency

HHS Department of Health and Human Services

MTBE methyl t-butyl ether

NCEH National Center for Environmental Health

NCHS National Center for Health Statistics

NHANES National Health and Nutrition Examination Survey

NHATS National Human Adipose Tissue Survey

NHEXAS National Human Exposure Assessment Survey

NIEHS National Institute of Environmental Health Sciences

NIH National Institutes of Health

NRC National Research Council

NTP National Toxicology Program

PBT persistent, bioaccumulative, and toxic

PCB polychlorinated biphenyls
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United States General Accounting Office

Washington, D.C. 20548

Health, Education, and

Human Services Division

B-282172 Letr

May 2, 2000

Congressional Requesters

State and local officials report continuing public concern over the health

risks posed by exposures to toxic chemicals, ranging from heavy metals

such as arsenic found at national hazardous waste sites to common

pesticides used in and around the home. For example, increasing rates of

cancer in various communities have prompted questions about the

potential link to residues from pesticides, indoor air pollutants, and other

toxic chemicals. Historically, estimates of human exposure to toxic

chemicals have been based on the concentration of these chemicals in

environmental media—such as air, water, and food—along with

assumptions about how people are exposed. Federal monitoring efforts

have primarily focused on this type of measurement. However, according

to public health experts, measurements of internal doses of exposure—

actual levels of chemicals or their metabolites1 in human tissues such as

blood or urine—can be a more useful measure of exposure for some

purposes.

Over the past decade, advances in laboratory technology have provided

new tools for measuring a broad range of chemicals in human tissues—

tools that can help researchers and health officials assess how much of a

chemical has been absorbed in the body and provide more accurate

measurements of exposure to relate to potential health risks. When

gathered for the U.S. population, such data can help identify new or

previously unrecognized hazards related to chemical substances found in

the environment, monitor changes in exposures over time, and establish

the distribution of exposure levels among the general population. These

data can also help identify subpopulations—such as children, low-income

groups, or ethnic minorities—that might be at increased risk because they

face particularly high levels of exposure. State and local health officials can

use information on typical exposures in the general population to help

assess environmental health risks for specific sites or populations within

their borders and to keep local residents informed. For example, local

officials in one community collected exposure measurements before,

1

Metabolites result from the interaction of the chemicals with enzymes or other chemicals

inside the body.
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during, and after the burning of arsenic-contaminated soil and found that

no excess exposure—as compared to typical levels found in the

population—had occurred.

In light of the potential benefits offered by these new technologies, you

asked us to review efforts to collect and use such information at both the

state and federal levels. Specifically, you asked us to (1) determine the

extent to which state and federal agencies—in particular, the Department

of Health and Human Services (HHS) and the Environmental Protection

Agency (EPA)—collect human exposure data2 on potentially harmful

chemicals, including data to identify at-risk populations, and (2) identify

the main barriers hindering further progress in such efforts.

We compiled a list of more than 1,400 naturally occurring and manmade

chemicals considered by HHS, EPA, and other entities to pose a potential

threat to human health. These included chemicals prioritized for safety

testing (based on EPA’s findings that the chemicals may present

unreasonable health risks), chemicals linked to cancer, toxic chemicals

frequently found at Superfund sites, and certain pesticides monitored in

foods or thought to be potentially harmful to humans. For these chemicals,

we assessed the extent to which major HHS and EPA survey efforts—

specifically HHS’ National Health and Nutrition Examination Survey

(NHANES) and EPA’s National Human Exposure Assessment Survey

(NHEXAS) phase I (pilot surveys)—were collecting human exposure data.

We also surveyed 93 environmental health officials in 50 states and the

District of Columbia, receiving responses from 81 officials in 48 states for a

response rate of 87 percent. At the federal level, we focused on survey data

collected for the general (non-occupationally-exposed) population. We

excluded federally sponsored academic and private sector research.

Appendix I explains our scope and methodology in more detail. We

conducted our work from March 1999 through March 2000 in accordance

with generally accepted government auditing standards.

2

The scientific community uses varying terminology when referring to human exposures.

Often, external contacts with chemicals are defined as “exposures,” and internal

measurements of exposure are referred to as “doses.” Doses are also considered a measure

of exposure. Our review focused primarily on efforts to gather internal exposure

measurements through human tissue in the non-occupationally-exposed population. To

simplify reporting, we are referring to such internal exposure measurements as “human

exposure” data.
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Results in Brief Federal and state efforts to collect human exposure data are limited,

despite some recent expansions. HHS and EPA have been able to take

advantage of improved technology to measure exposures for more people

and for a broader range of chemicals. Still, with existing resources, HHS

and EPA surveys together measure in the general population only about 6

percent of the more than 1,400 toxic chemicals in our review. For those

toxic chemicals that we reviewed, the portion measured ranged from 2

percent of chemicals prioritized for safety testing to about 23 percent of

those chemicals most often found at Superfund sites and considered to

pose a significant threat to human health. Even for those chemicals that are

measured, information is often insufficient to identify smaller population

groups at high risk, such as children in inner cities and people living in

polluted locations who may have particularly high exposures. At the state

level, efforts are similarly limited. Almost all state officials who we

surveyed said they highly valued human exposure data for populations

within their borders, and many provided specific examples of how such

data have provided useful information for interpreting citizens’ health risks

and guiding public health actions. For example, state officials in nine states

used human samples not only to identify who was exposed to a toxic

pesticide illegally sprayed in citizens’ homes, but to identify houses most in

need of clean-up. Despite this perceived value, most officials reported that

they were unable to collect or use human exposure data in most of the

cases where they thought it was important to do so.

Three main barriers limit federal and state agencies’ abilities to make more

progress. First, federal and state laboratories often lack the capacity to

conduct measurements needed to collect human exposure data;

additionally, for most of the chemicals on our list, no laboratory method

has been developed for measuring the chemical levels in human tissues.

The second barrier, particularly voiced by state officials, relates to the lack

of information to help set test results in context. Public health officials said

they need more information on typical exposures in the general population

so that they can compare this information with people’s levels at specific

sites or with specific populations in their states. They also said they needed

more research to relate exposure levels to health effects for the chemicals

of concern in their states. The third barrier, of particular concern at the

federal level, is that coordinated, long-term planning among federal

agencies has been lacking, partly because of sporadic agency commitments

to human exposure measurement and monitoring. HHS and EPA officials

indicated that they have been discussing the merits of establishing a

coordinated interagency human exposure program, but they have not yet
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formalized or agreed upon a long-term strategy. A long-term coordinated

strategy should also ensure adequate linkages between collection efforts

and agency goals, provide a framework for coordinating data collection

efforts that considers individual agencies’ needs and expertise, provide a

framework for identifying at-risk populations, and consider states’ needs

for information. To address these needs, we are recommending that the

Secretary of HHS and the Administrator of EPA develop a coordinated

federal strategy for the short- and long-term monitoring and reporting of

human exposures to potentially toxic chemicals.

Background EPA projects a continuing upward trend in environmental compliance

costs for pollution control measures, amounting to an estimated $148

billion this year. Hundreds of millions of dollars are spent monitoring levels

of toxic chemicals in the environment—for example, approximately $139

million of federal funding supported national air-quality monitoring

networks in the United States in fiscal year 1999.3 Despite these

expenditures, what often is not known is the extent to which people are

exposed to potentially harmful chemicals in their daily lives, the chemicals

to which they are most often exposed, the levels of such exposure, how

exposures change over time in relation to regulatory policies, and the

sources of exposure. Policymakers, regulators, researchers, and public

health officials must often rely on estimates of human exposure levels for

the general population or for smaller groups thought to be at risk. Such

estimates are often derived from data showing the extent the chemicals are

found in the air, water, food, or other environmental media and

assumptions about how and at what rate the body absorbs the chemicals it

contacts. A variety of methods for measuring exposures are considered to

be more direct than those that measure chemicals in the ambient

environment. These methods measure exposures in people’s more

immediate environments and include tools such as personal air monitors,

which measure chemicals that may be inhaled. For several chemicals and

purposes, measuring internal exposure levels in human tissues is

considered the most useful and accurate measure and an important piece

of the information needed to link contaminants in the environment with

adverse health effects.

3

The Role of Monitoring Networks in the Management of the Nation’s Air Quality, National

Science and Technology Council, Committee on Environment and Natural Resources, Air

Quality Research Subcommittee (Mar. 1999).
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While officials may be able to collect internal exposure levels at a local

level, the results are difficult to interpret without information such as

comparative data to show what exposure levels might be considered high

or research findings linking exposure levels to specific health effects.

Because of the need for improved data on actual human exposures found in

the general population, the National Research Council (NRC), an arm of the

National Academy of Sciences, recommended in 1991 that the nation adopt

a new program to monitor chemical residues in human tissues, such as

blood. NRC noted that determining the concentrations of specific

chemicals in human tissues could serve to integrate many kinds of human

exposures across media such as air, water, or food and over time. As one

component of an effort to manage environmental quality and protect public

health, NRC reported that a well-designed national program for monitoring

toxic chemicals in human tissues was needed.4 NRC pointed out that

human exposure data could be used to help monitor changes in the

population’s exposure to chemicals and identify population groups—by

factors such as age or geographic location—that might be at increased risk

because they face higher levels of exposure.

Direct biological monitoring of human exposure to chemicals has been

made increasingly possible by recent advancements in analytical chemistry

and molecular biology. Methods have been developed to measure smaller

levels of toxicants in body tissues and to do so with smaller sample

amounts.5 For example, a few years ago a laboratory would need 100

milliliters of blood to detect dioxins in the part-per-billion range. New test

methods use less than 10 milliliters and are capable of detecting

concentrations in the parts-per-trillion range. Single samples can also now

be used to detect low concentrations of multiple chemicals. Since 1995, for

example, laboratory methods have been developed to detect polycyclic

aromatic hydrocarbons, a group of more than 100 chemicals formed during

4

According to NRC, human monitoring data alone can signal the need to conduct studies on

specific environmental chemicals, but these data are best viewed as one component of a

comprehensive environmental monitoring program. Human measurements are best

supplemented with knowledge of contaminant sources, environmental pathways,

environmental concentrations, time patterns and locations of exposure, routes of entry into

the body, material toxicity, and latency. See NRC, Commission on Life Sciences, Monitoring

Human Tissues for Toxic Substances (Washington, D.C.: National Academy Press, 1991).

5

Other human biological tissues that might be used for measurements of chemical

concentrations include fat tissue, breast milk, semen, urine, liver specimens, hair,

fingernails, or saliva. Human breath has also been used to measure exposure to certain

chemicals.
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the incomplete burning of coal, oil, gas, garbage, tobacco, and other

substances.

Lead is an example of a chemical that has been monitored extensively by

measuring absorption into human tissues—specifically, lead levels in the

blood. Elevated levels of lead in the blood can cause learning problems

and, at extreme levels, result in serious brain or kidney damage. Data on

blood lead levels have been collected for the national population since

1976. Public health officials, researchers, and others have used lead

exposure data from large- and small-scale studies in many ways to identify

at-risk populations, evaluate regulatory actions, improve the models used

to estimate exposure, and identify significant sources of preventable

exposure, as shown in the following examples.

• Identifying at-risk populations: National blood lead data revealed that

low-income children living in houses built before 1946 had a prevalence

of elevated blood lead levels of 16.4 percent as compared to 4.4 percent

for all children ages 1 through 5; non-Hispanic black children in similar

housing had a prevalence of 21.9 percent—the highest risk of elevated

blood lead levels of any demographic group. Using this information,

state and local health officials can more effectively target screening and

treatment efforts.

• Establishing and evaluating public health-related policies: In the 1980s,

EPA was considering whether or not to make permanent a temporary

ban on lead in gasoline. National data on lead exposure showed a

decline in average blood lead levels that corresponded to the declining

amounts of lead in gasoline. Based on this and other information, EPA

strengthened its restrictions on lead in gasoline and required a more

rapid removal of lead from gasoline.

• Improving models used to estimate exposure: Experts indicate that an

increasingly important use of human exposure data has been as a

“reality check” on other indexes of exposure, such as questionnaires

about activities or work histories, to ascertain whether exposures may

have occurred. For example, prior to the decision to phase out lead in

gasoline, exposure models suggested that eliminating lead in gasoline

would have only a slight effect on blood lead levels, while actual testing

showed a more dramatic effect.

• Identifying key sources of exposure: When combined with other

exposure data, exposure measurements can help reveal the source of

the exposure—an essential step in developing and monitoring

intervention strategies designed to reduce or eliminate harmful

exposures. For example, when no evidence of lead paint—the most
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common source of lead contamination—was found in the home of a

child whose blood showed abnormal levels of lead, public health

officials were baffled. Observational data on how and where the child

spent time and environmental data from the surfaces most often

encountered revealed that lead-contaminated stuffing in a toy the child

chewed likely accounted for the high exposure. The child’s blood lead

level declined when the contaminated toy was removed.

While lead is unique among chemicals in that it has been extensively

studied—decades of research has shown its harmful effects at increasingly

lower levels—such research has been possible in part because of

laboratory advances in measurement technology. Over the years, as

technology improved the ability to measure smaller and smaller amounts of

lead in the bloodstream, researchers have been able to identify increasingly

subtle adverse effects by linking blood lead levels and changes in

neurobehavioral functioning.

Current Measurement

Efforts Cover Few

Chemicals and

Situations

Although HHS and EPA each are expanding their survey efforts to use new

technologies and measure a broader range of exposures in the national

population, their measurement efforts cover a limited portion of the more

than 1,400 potentially harmful chemicals we reviewed. These surveys also

remain of limited value for identifying at-risk populations, because in the

case of their survey efforts, sample sizes to date have been insufficient—

and, for most chemicals, not representative of the general population. In

addition, federal efforts to help assess potential disproportionate

exposures by collecting data on communities living near Superfund sites

have been limited to few locations. State agencies reported that their

efforts are also limited, despite the importance they place on using such

data in their studies of population- or site-specific situations within their

borders. According to state environmental health officials, they are often

unable to collect these data.

Federal Efforts Are

Expanding

In our examination of the HHS and EPA surveys, we found that the types of

chemicals measured have recently increased. For the past 40 years, HHS’

Centers for Disease Control and Prevention (CDC) has collected through a

survey nationally representative data on the health and nutrition of the U.S.

population. Exposure measurements are one component of this survey. In

the mid-1990s, EPA’s Office of Research and Development initiated a

human exposure survey, which is currently in its pilot phase in three

locations across the country. A third more recent effort to monitor human
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exposures to select chemicals was initiated in 1996 by HHS’ National

Institute of Environmental Health Sciences (NIEHS) of the National

Institutes of Health (NIH). For each of these federal efforts, laboratory

measurements are largely conducted by the laboratory at CDC’s National

Center for Environmental Health, which also developed many of the

methods for performing these measurements.

CDC’s National Health and

Nutrition Examination Survey

CDC collects human exposure data as part of NHANES, which has been

conducted periodically since 1960 and, beginning in 1999, has been

conducted annually. NHANES monitors trends in health status by

conducting interviews and physical assessments on a nationally

representative sample of about 5,000 people per year. NHANES collects

blood and urine samples for many purposes, such as assessing cholesterol

levels and the prevalence of diabetes. Since 1976, these samples have also

been used to measure exposure to selected chemicals, and excess samples

are banked for future research. In the past, CDC’s human exposure

monitoring efforts have focused largely on lead, cadmium, and a few

pesticides and volatile organic compounds—chemical compounds which

include a number of animal and known or suspected human carcinogens

found in tobacco smoke, building supplies, and consumer products.6

Starting with the 1999 NHANES, CDC proposed to measure up to 210

chemicals in human tissues as staff and other resources permitted. These

chemicals include metals such as mercury, which at high levels may

damage the brain, kidneys, and developing fetus; polyaromatic

hydrocarbons (a group of compounds found in sources such as foods that

have been grilled); and volatile organic compounds, such as benzene. At

the time of our review, a CDC official indicated that resources allowed

them to include about 74 chemicals for 1999 and 2000. The estimated

marginal costs for the environmental exposure-related components of the

NHANES 1999 survey were about $5 million.

EPA’s National Human Exposure

Assessment Survey

To expand upon and replace its National Human Adipose Tissue Survey

(NHATS)—a tissue monitoring program, which ended in 1992—EPA

6

Special reference studies supported by the Agency for Toxic Substances and Disease

Registry were also conducted on nonrepresentative samples of a portion of the people

participating in the most recently completed segment of NHANES (conducted from 1991

through 1994). These special studies assessed exposure to 45 pesticides and volatile organic

compounds.
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initiated in 1993 pilot surveys for NHEXAS in three regions of the country.7

A goal of the NHEXAS pilots is to obtain knowledge on the population’s

distribution of total exposure to several classes of chemicals and to test the

feasibility of collecting representative survey data on people’s total

exposures. NHATS focused on monitoring human fat tissues for persistent

organochlorine pesticides and polychlorinated biphenyls (PCB); NHEXAS

has broadened this focus in two ways. First, in addition to measuring

chemical levels in samples such as blood or urine, the NHEXAS pilot

surveys included measurements of chemicals in air, foods and beverages,

water, and dust in individuals’ personal external and internal environments.

To conduct these measurements, the pilot surveys used tools such as

questionnaires, activity diaries, air-monitoring badges worn by the

individual or other air-monitoring devices, and tap and drinking water and

food samples. Such data are important for purposes such as identifying the

most important sources or routes of exposure and for taking actions to

reduce or prevent exposures. Second, the NHEXAS pilot surveys included

more types of chemicals than pesticides, such as lead and other heavy

metals. The NHEXAS pilots, however, included fewer chemicals than its

predecessor—which measured about 130 pesticides and PCBs in human fat

tissue—in part because monitoring levels of any given chemical in personal

environments and in human tissues requires significantly more laboratory

measurements for the same chemical. EPA’s NHEXAS pilot surveys, which

have tested biological samples from about 460 participants, have

collectively measured up to 46 chemicals, including pesticides, heavy

metals, and volatile organic compounds in blood, urine, or hair. Once data

from these pilot surveys have been further analyzed, EPA intends to assess

the feasibility and cost of conducting a national effort to collect total

exposure data. To date, EPA has invested about $20 million to support the

pilot surveys. Very preliminary estimates by EPA for a national survey

range from $20 million to $30 million per year over 10 years or more.

National Institute of

Environmental Health Sciences’

Human Exposure Initiative

In 1996, NIEHS began an initiative to collect human exposure data. This

initiative was started as a collaboration between NIEHS and CDC to

improve understanding of human exposures to hormonally active agents—

also called “environmental endocrine disrupters”—for the national

7

Specifically, pilot surveys were conducted in Arizona, Maryland, and EPA’s region 5

(Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin).
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population.8 The effort was intended to build upon the chemical monitoring

in NHANES by supporting the development of laboratory methods and

measurement of previously unmeasured chemicals in human tissues

collected from NHANES and other studies. NIEHS and CDC signed an

interagency agreement, under which CDC will develop methods for

measuring and will measure in blood, urine, or both up to 80 chemicals

thought to be hormonally active agents. For this effort, CDC obtained

samples of about 200 people—most of whom are from the ongoing

sampling of the general population under NHANES.

In 1999, officials of NIEHS and the National Toxicology Program (NTP)—

an interagency effort to coordinate toxicological research and testing

activities of HHS, which is administratively housed at NIEHS—proposed to

expand upon the initial collaboration and formalized the undertaking as the

Human Exposure Initiative. Specifically, they proposed a broader

interagency effort to quantify human internal exposures to chemicals

released into the environment and workplace. One significant purpose of

this effort was to help prioritize those chemicals and chemical mixtures to

be studied by NTP, recognizing the limited resources available for

toxicological testing and the need for better information to prioritize which

chemicals should be tested. According to NTP officials, although NTP is the

nation’s largest federal toxicology testing program, it can initiate only 10

long-term cancer studies and 10 reproductive studies per year.9 NIEHS

provided a list of 131 chemicals it hoped would be measured through this

expanded effort. At the time of our review, however, program officials told

us that NIEHS had not published data from the chemicals CDC had

measured under this agreement, and CDC was developing the laboratory

methods needed to measure many of the chemicals identified by NIEHS as

8

The concern about endocrine disrupters originated from the finding that some synthetic

chemicals in the environment are associated with adverse reproductive and developmental

effects in wildlife and mimic the actions of female hormones. According to NRC, although it

is clear that exposures to hormonally active agents at high concentrations can affect wildlife

and human health, the extent of harm caused by exposure to these compounds in

concentrations that are common in the environment is debated. See NRC, Commission on

Life Sciences, Hormonally Active Agents in the Environment (Washington, D.C.: National

Academy Press, July 1999).

9

According to NTP officials, chemicals are tested for cancer and noncancer endpoints—

including effects on reproduction, development, nervous system, and immune systems—

using traditional bioassays as well as newly validated tests. Validation of new tests is

achieved through an NTP interagency center involving 15 federal agencies or institutes.
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needed.10 (For more information on NHANES, NHATS, NHEXAS, and

NIEHS’ Human Exposure Initiative, see app. II.)

Despite Expansion,

Chemicals Covered in

Exposure Measurements

Remains Limited

Despite these expanded efforts, NHANES and the NHEXAS pilot surveys

cover only about 6 percent (or 81) of the 1,456 potentially harmful

chemicals in our review. We compared the chemicals measured by these

surveys to eight selected lists of chemicals of concern.11 Our selection was

based, in part, on our assessment and input from experts that these lists

contained chemicals of higher concern to human health.12 However, the

listed chemicals represent a small portion of those that are regulated or are

of potential public health importance. For example, there are over 7,000

lists of chemical substances and classes that are regulated under the Toxic

Substances Control Act and the Emergency Planning and Community

Right-to-Know Act.

For those individual lists that we reviewed, the portion of toxic chemicals

measured ranged from 2 percent of chemicals prioritized for safety testing

(based on EPA’s findings that the chemicals may present unreasonable

risks) to about 23 percent of chemicals most often found at the nation’s

Superfund sites and identified as posing the most significant threat to

human health. See table 1 for each of the lists reviewed and the extent to

which NHANES or the NHEXAS pilots are measuring these chemicals, and

appendix I for a discussion of each list included in our review.

10CDC officials indicated that, by the end of 1999, it had developed laboratory methods to

measure more than half of the chemicals under the agreement with NIEHS.

11We excluded NHATS and Human Exposure Initiative chemical lists from our analysis.

NRC’s 1991 review of the NHATS program raised questions about the representativeness of

the results and the methods used to handle the tissue specimens, among other questions.

The Human Exposure Initiative measurements were not available at the time of our review

and, thus, which chemicals had been or are currently being measured was not known.

12We selected these lists based on input from program officials and experts at EPA, HHS, the

Association of Public Health Laboratories, and the Pew Commission on Environmental

Health and our assessment that the criteria for listing a chemical demonstrated that

exposure could potentially be harmful to humans. There are many toxic chemical lists

maintained by different programs and agencies for different purposes that we did not

include in our review and, as such, the ones we reviewed do not necessarily individually or

collectively represent the chemicals of highest concern to human health.
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Table 1: Extent to Which Human Exposure Data Are Collected for Potentially Harmful

Chemicals Through NHANES or the NHEXAS Pilot Surveys

Note: Our analysis was based on human exposure data collected through NHANES or the NHEXAS

pilot surveys through 2000.

a

The Report on Carcinogens list may also include pharmaceutical agents, substances of primarily

occupational concern, and banned substances. According to NIEHS officials, this may account for their

lower inclusion in NHANES or the NHEXAS pilots. NIEHS and NTP officials indicated that, in addition

to these chemicals, NTP reports results of its chronic bioassays for cancer in its technical report series.

There are now approximately 500 reports, which collectively include nearly 250 chemicals found to

cause cancer in rodents. Officials indicated that another useful evaluation would assess the proportion

of rodent carcinogens for which human exposure data are collected and that NTP is planning to

conduct such an evaluation.

While many potentially harmful chemicals in these lists are not measured in

the population, NHANES or the NHEXAS pilot surveys contain a greater

portion of chemicals considered of higher priority. Two toxic chemical lists

we reviewed—one ranking chemicals frequently found at Superfund sites

and one ranking selected chemicals compiled by EPA—prioritized

chemicals based on their potential to harm human health. We examined the

highest-ranked chemicals on these lists and found that higher proportions

of these chemicals were or will be measured compared to the overall list. A

CDC laboratory official also indicated CDC was in the process of

Priority chemicals

Chemicals

measured or being

measured

Description of list

Number

in list Number Percent

Chemicals found most often at the national Superfund

sites and of most potential threat to human health 275 62 23%

EPA’s list of toxics of concern in air 168 27 16

Chemicals harmful because of their persistence in the

environment, tendency to bioaccumulate in plant or

animal tissues, and toxicity 368 52 14

Pesticides of potential concern as listed by EPA’s

Office of Pesticide Programs and the U.S.

Department of Agriculture’s Pesticide Data Program 243 32 13

Chemicals that are reported in the Toxic Release

Inventory; are considered toxic; and are used,

manufactured, treated, transported, or released into

the environment 579 50 9

Chemicals that are known or probable carcinogens as

listed in HHS’ Report on Carcinogensa 234 17 7

Chemicals most in need of testing under the Toxic

Substances Control Act (Master Testing list) 476 10 2
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developing methods to measure a number of the chemicals on these lists

and planned to measure other chemicals in future efforts if they have

adequate resources to do so.

• Ranking of chemicals frequently found at Superfund sites: Developed by

EPA and HHS’ Agency for Toxic Substances and Disease Registry

(ATSDR), which conducts public health assessments or other health

investigations for populations living around national Superfund sites,

this list ranks substances that are most commonly found at Superfund

sites and pose the most significant potential threat to human health due

to their known or suspected toxicity and potential for human exposure.

Of the top 40 chemicals on this list, CDC indicated that 9 were currently

being measured in NHANES. CDC hopes to include an additional 30 of

the top 40 in future efforts; 11 of these 30 chemicals, however, were

included in the NHEXAS pilot surveys.

• Ranking of selected toxic chemicals compiled by EPA: These rankings

are based on a chemical’s persistence, tendency to accumulate in plants

and animals, and toxicity. CDC indicated 4 of the top 22 chemicals on

this list based on their health hazard13 were currently being measured in

NHANES. CDC hopes to include the remaining 18 in future efforts; 6 of

the 18 chemicals were included in the NHEXAS pilot surveys.

Federal Efforts Are Limited

for Identifying At-Risk

Subpopulations

In recent years, federal agencies have been charged with identifying

whether certain populations—including minorities, people with low

incomes, and children—disproportionately face greater health risks

because they have greater exposure to environmental hazards.14

Researchers increasingly recognize that the scarcity of adequate and

appropriate data, especially for exposures and related health effects,

13EPA’s prioritized chemical list ranks chemicals based on the length of time to break down,

the degree to which they accumulate in plants and animals, and their toxicity. Both

ecological and health risk scores are calculated. We used only the health risk scores in our

analysis.

14Executive Order 12898 requires that each agency identify and address as appropriate

disproportionately high and adverse human health or environmental effects of its programs,

policies, and activities on minority populations and low-income populations in the United

States and its territories and possessions. Executive Order 13045 established similar

requirements with respect to children.
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hinders efforts to more systematically identify groups that may be at risk.15

Lacking such data, past efforts to identify the exposures of certain

demographic groups have often relied on measures of chemical levels in

the surrounding environment. For example, some studies around

hazardous waste sites and industrial plants have shown that minorities and

low-income subpopulations are disproportionately represented within the

geographic area around the sites. Such studies are limited in identifying the

actual health risk because they must make assumptions about how these

substitute measures, such as how close one lives to a hazardous waste site,

relate to actual exposures experienced by people.

To identify groups whose exposure is disproportionately greater than that

experienced by the remainder of the population—and thereby provide

more definitive assessments of whether certain groups potentially face

greater health risks—health officials and researchers might measure

exposure levels for (1) a representative sample and analyze the

characteristics of subpopulations with the highest exposures or (2) a

population thought to be at high risk and compare it to measurements from

a reference population.16 We examined the extent to which federal survey

data on human exposures collected to date could be used to assess

characteristics of those groups most exposed. We also examined the extent

to which human exposure data was collected on a population considered to

be at higher risk—specifically, those living around national priority

hazardous waste sites. In each effort, the information collected has been

limited, as discussed below.

Sampling Not Sufficient to

Identify Many Highly Exposed

Groups

Representative sampling is required to identify at-risk subpopulations in a

non-biased way—that is, without presupposing that a certain group is at

higher risk. The sample must also be large enough to ensure highly exposed

15S. Perlin, K. Sexton, and D. Wong, “An Examination of Race and Poverty for Populations

Living Near Industrial Sources of Air Pollution,” Journal of Exposure Analysis and

Environmental Epidemiology, Vol. 9, No. 1 (1999), pp. 29-48.

16D. Wagener, D. Williams, and P. Wilson, “Equity in Environmental Health: Data Collection

and Interpretation Issues,” Toxicology and Industrial Health, Vol. 9, No. 5 (1993), pp. 775-95.
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subpopulations can be objectively identified.17 For nearly all chemicals

except lead, however, past federal collection of human exposure data in

NHANES and the NHEXAS pilot surveys has been insufficient to identify

whether disproportionate exposures are occurring in many demographic

groups. In the case of NHANES, the sample is generally drawn to reflect the

national population as a whole.18 Consequently, the sample of the group of

interest may be too small to draw meaningful conclusions about

characteristics, such as exposures, of the group. In the past, most NHANES

exposure measurements were conducted among non-randomly-selected

samples and from only a portion of the surveyed participants, thus limiting

the ability to identify highly exposed groups. Lead was an exception. Data

for blood lead levels in children have been the most comprehensively

collected, and certain characteristics have been clearly associated with a

higher prevalence of blood lead levels. EPA has concluded that the

evidence is unambiguous: children of color have a higher prevalence of

elevated blood lead levels than white children do, and children in lowerincome families have a higher prevalence than children in higher income

families. See table 2 for the most recent NHANES analysis.

17The feasibility of using a representative survey to identify at-risk subpopulations based on

individual characteristics (such as age, race, or income level) or location (such as a city,

county, or state) depends on sample design and size—that is, on how the participants are

selected and how many participants are included. Generally, the lower the percentage of the

population in question in the sample, the less the data can be used to develop precise

estimates of exposure or to distinguish exposure levels between subgroups.

18Certain groups may be included at a higher rate or oversampled to ensure a greater level of

accuracy. For example, between 1988 and 1994, children ages 2 months through 5 years

surveyed in NHANES were oversampled.
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Table 2: Prevalence of Elevated Blood Lead Levels in Children Ages 1 Through 5, by

Selected Demographic Characteristics (NHANES, 1991 Through 1994)

Source: CDC, “Update: Blood Lead Levels—United States, 1991-1994,” Morbidity and Mortality

Weekly Report, Vol. 46, No. 7 (1997), pp. 141-5.

CDC officials told us that representative data, such as that collected for

lead, would be collected for a larger number of chemicals starting in 1999.

However, CDC plans indicated that for most chemicals monitored, only a

portion of NHANES survey participants—generally one-third or fewer,

depending on the type of chemical—would be tested. For some chemicals,

only certain groups thought to be at higher risk may be tested. For

example, NHANES will include measurement of certain persistent

pesticides known as organochlorines in one-third of the survey participants

ages 12 through 19. Children under 12 will not be assessed.19 CDC officials

indicated that people over 19 may be assessed if adequate resources are

available to do so. Although most organochlorines are banned in the United

States, some are still used in home and garden products, such as products

for treating lice and controlling agricultural and structural pests and flame

Characteristic of children in sample

Percentage with elevated

blood lead levels

Race/ethnicity

Black, non-Hispanic 11.2%

Mexican-American 4.0

White, non-Hispanic 2.3

Income level

Low 8.0

Middle 1.9

High 1.0

Age group

1 through 2 5.9

3 through 5 3.5

Total ages 1 through 5 4.4%

19According to CDC officials, children under 12 will not be assessed because the volume of

tissue samples needed to perform the measurement will not be available. Other

measurements—such as those for lead, mercury, and cotinine (a metabolite of nicotine

illustrating exposure to cigarette smoke)—will be performed for many in this age group.
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retardants used in synthetic fabrics.20 NHANES data from a one-third

subsample will be useful for establishing reference ranges within the

population and illuminating exposure levels nationally; they will also be

useful for identifying exposures of broad demographic groups, such as

males and females. But these data are not enough to enable researchers to

assess exposure levels of or characterize many potentially at-risk groups,

such as the exposures of inner-city children in low-income families.21

According to a CDC laboratory official, targeted studies should be

considered for groups that represent a small portion of the population.

Similarly, the NHEXAS pilot surveys included representative samples of

participants in the three geographic locations covered. However, because

of the smaller sample sizes, the work to date has also been too limited for

20According to CDC laboratory officials, other NHANES exposure measurements planned

for 1999 and 2000 for a subsample of participants includes volatile organic compounds,

mercury, nonpersistent pesticides, phthalates, and trace metals. Air toxic exposures to

selected volatile organic compounds will be measured in personal measurements—such as

chemical levels in the air, measured through badges, and chemicals in water samples—and

in blood samples from a subsample of people ages 20 through 59. Mercury will be measured

in the hair and blood of participants ages 1 through 5 and women ages 16 through 49.

Nonpersistent pesticides or their metabolites are planned for measurement in one-half of

participants ages 6 through 11 and one-third of participants ages 12 and over. Surveys and

focused research indicate that household use of certain pesticides may be extensive, but

little information is available concerning residential or household exposures among the

general population. Phthalates are planned for measurement in one-third of the participant

ages 6 and older. Seventeen trace metals will be measured in one-third of participants ages 6

and older. Trace metals such as barium and beryllium have been associated with adverse

health effects in occupational or laboratory studies but have not been monitored in the

general population.

21The current design of NHANES samples allows several years of data to be combined. If

exposure for chemicals is measured consistently over several years, then assessing risk

factors may be increasingly possible over time. CDC officials indicated that for any annual

NHANES full sample, a limited number of estimates for broad population subgroups can be

developed. More detailed measures for smaller subgroups (for example, analyses by age,

gender, and race and ethnicity) will require more years of data, generally 3 through 6 years—

and even longer if a subsample is used—of data collected for all participants. Based on an

annual sample of one-third of the participants, CDC indicated that estimates may be

possible for very broad subgroups, such as males or females; participants ages 6 through 19

or over 20; or a few major race and ethnicity groups, depending on the prevalence of the

condition examined.
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much analysis of at-risk populations.22 The pilot surveys included biological

measurements for about 200 people in six Midwestern states, about 180

people in Arizona,23 and about 80 people in Baltimore.

Federal Efforts to Identify

Communities of Concern

Valuable, but Human Exposure

Data Are Limited

A second method to identify a subpopulation disproportionately at risk of

adverse health effects is to compare exposure levels for a group thought to

be at high risk with baseline measurements from a reference population.24

This method can be used to determine, for example, the extent to which

people in a neighborhood, community, or geographic location are exposed

relative to others. In cases where exposure levels have been identified as

high compared to reference populations but potential health effects

associated with those levels have not been researched, public health

actions can help prevent further or increasing exposures, and these groups

can be assessed for any subsequent health outcomes.

22One assessment of the data from Midwestern states provided some indication of potential

differences in personal exposures between age groups, races, income segments, and house

construction dates. Researchers cautioned that the data for some categories examined were

small. This assessment did not report on exposure measurements from biological sampling

in this survey. (See E. D. Pellizzari, R. L. Perritt, and C. A. Clayton, “National Human

Exposure Assessment Survey: Exploratory Survey of Exposure Among Population

Subgroups in EPA Region V,” Journal of Exposure Analysis and Environmental

Epidemiology, Vol. 9 (1999), pp. 49-55.

23These participants provided biological samples, such as blood and urine. Larger

participant groups in the study areas provided environmental and food monitoring samples

and responded to questionnaires. This excludes a related but separate study done in

Minnesota reviewing pesticide exposures that was not one of the three formal pilot surveys.

24Determining the distribution of chemical exposure among a non-occupationally-exposed

population establishes a “reference range” that shows what can be considered background

exposure and what can be considered high. With reference range information, officials

concerned about exposures of groups can compare the groups’ exposures to those of the

general population and determine whether public health action is warranted to prevent or

reduce high levels of exposure.
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One federal effort, conducted by ATSDR, analyzes risks faced by

communities near hazardous waste sites. ATSDR estimates that 12.5

million people live within 1 mile of the nation’s 1,300 Superfund sites. The

agency can collect biological samples through exposure investigations as

part of the public health assessment process or in response to requests

from the public.25 ATSDR officials said that human exposure data collected

at Superfund sites have been useful in deciding on actions such as stopping

or reducing exposures, relocating residents, referring residents for medical

follow-up, reducing community anxiety, influencing priorities on sitespecific clean-up, making referrals to researchers for assessing health

links, and educating community and other health providers. As evidence,

they pointed to the conclusions of an expert review panel, which stated in

March 1997 that human exposure data were as important to exposure

investigations and public health assessments as environmental monitoring

results at the sites of concern.26 However, the number of investigations that

included human exposure data has been limited. Between 1995 and July

1999, ATSDR had gathered biological samples at only about 47 of the more

than 1,300 Superfund sites. At least 34 of these investigations detected

contaminants in people and 16 found elevated levels.

Other federally conducted efforts designed to monitor or collect data on

the exposures of populations within selected communities or geographic

regions have also been infrequent.27 One such regional-scale effort under

way is collecting data on exposures within selected communities along the

border between Texas and Mexico. Officials from Mexico and federal and

state agencies in the United States are comparing exposures of people in

25ATSDR conducts exposure investigations when (1) people have likely been exposed to a

contaminant, (2) more information is needed on the exposure, (3) an exposure investigation

will provide that information, and (4) that investigation will affect public health decisions.

26In its report, panel members suggested many improvements to ATSDR’s exposure

investigations, including creating a technical planning group to review emerging and

innovative technologies and establishing a national clearinghouse of collected data. ATSDR

officials indicated that they had not been able to act on some of the panel’s suggestions

because of limited staff and resources and other barriers to collecting data, such as the lack

of laboratory methods for testing chemicals of interest. ATSDR has nine staff to conduct

exposure assessments for sites across the nation and can only respond to requests from

communities or state or local officials for assistance rather than conducting such

assessments as part of every new investigation.

27Federal agencies also might fund academic research that is designed to identify

communities of concern. Assessing the extent that federally supported academic research

included or focused on human exposure data to identify at-risk population was beyond the

scope of our review.
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the border area with those in areas away from the border. Another study

examined the exposures of people along the Arizona border compared to

the exposures of people elsewhere in the state. This study collected

environmental samples for pesticides, metals, and volatile organic

chemicals. Blood and urine samples were also tested to relate the

environmental measurements to the measurements in human tissues for

these chemicals.

State Officials Value Human

Exposure Data for Studies

and Investigations but Do

Not Often Include Them

Most state officials who we surveyed highly valued human exposure data.

However, most could not include it in their exposure-related health studies,

investigations of concerns such as disease clusters, or surveillance efforts.

Almost half of the officials responding to our survey estimated that they

had participated in 10 or more exposure-related studies or investigations

since 1996, with about 16 percent estimating they participated in 50 or

more. However, about half of officials indicated they could seldom if ever

collect exposure data through human samples in their efforts. When data

were developed, officials listed five main uses: (1) environmental health

epidemiologic studies, (2) surveillance of diseases or conditions with

suspected environmental causes, (3) investigations of citizen concerns, (4)

planned or accidental chemical releases, and (5) disease clusters (see table

3).28 State officials we spoke with noted that human exposure data are

often the most valid and persuasive evidence available to demonstrate

whether, and to what extent, exposure has occurred or changed over time.

In highly charged situations, where community trust has eroded, such data

may be the only evidence acceptable to area residents.

28Since most states conduct surveillance for lead exposure, we asked officials to not include

these efforts in their responses. See app. III for a copy of our survey.
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Table 3: Examples of How State Officials Use Human Exposure Data

While mercury, arsenic, and pesticides were most often reported as being

studied in human samples, some state officials reported using human

exposure data for chemicals that CDC has since 1991 developed methods

to measure. For example, about 15 percent of officials conducted studies of

human exposure to volatile organic compounds, and almost 30 percent

reported studies of exposure to PCBs using data from tissue analysis.

Regardless of whether state officials had collected or used human

exposure data in the past 4 years, about 90 percent of those officials

responding to our survey said human exposure data from tissue samples

was extremely or very important for addressing environmental health

concerns. Despite the perceived value of such data, almost two-thirds of

officials said they could include human exposure data in fewer than half of

the exposure-related studies, investigations, and surveillance efforts where

Purpose Example

Environmental health

epidemiologic studies

Using blood and urine samples from people who ate sport fish and were concerned about undue

exposure to dioxins, pesticides, and other chemicals, health officials determined these people had

exposure to some chemicals from 2 to 10 times higher than levels in a reference population. Based on

these results, officials will focus a larger health effects study on exposure to those chemicals.

Surveillance of diseases or

conditions with suspected

environmental causes

Virtually all states collect information on blood lead levels in children to monitor and prevent lead

poisoning. Some also monitor exposure to pesticides and other chemicals such as mercury and arsenic.

Investigation of citizen

concerns

Health officials used human tissue measurements and citizens’ reports of illnesses to demonstrate that

the combined effect of chemicals released into the environment posed a health hazard severe enough to

warrant evacuating nearby residents. State and federal officials subsequently closed a manufacturing

plant because of the harmful health effects of its chemical releases.

Investigation of planned or

accidental chemical releases

Officials in nine states asked CDC to test tissue samples from almost 17,000 individuals thought to have

been exposed to methyl parathion, a deadly pesticide. CDC’s ability to measure the pesticide in human

tissue and compare exposures across states was critical to identifying individuals with high exposures

and houses most in need of clean-up. Because relocating residents and removing the pesticide from

homes cost up to $250,000 per household, the exposure data helped officials avoid spending limited

funds on houses that did not pose a health risk to the people living in them. One state official said the

exposure results reduced the number of houses needing pesticide removal from hundreds to fewer than

10.

Investigation of disease

clusters

State health officials reviewed data on individual cases of cancer in one community and for the entire

state. When available data on known risk factors did not account for the increased incidence of breast

cancer, officials began a more detailed study that included human tissue analysis. Blood samples were

obtained from women before and after treatment began and from women in a control group. Results will

be compared to reference range data developed by CDC. One goal of such studies is to help identify

environmental factors that contribute to breast cancer risk.
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they considered it important. More than one-third said they seldom could

include such data.

Several state health and laboratory officials whom we interviewed

expressed frustration at the missed opportunities for collecting biological

samples as part of their studies and investigations for reasons such as

limited laboratory capacity. For example, health officials in one state could

not examine the role played by methyl t-butyl ether (MTBE)—an additive

designed to promote more efficient burning of gasoline—in a major

respiratory disease outbreak because state staff lacked the expertise and

CDC staff lacked the time to conduct the needed tests. In 1995, after MTBE

was added to gasoline and thousands of citizens reported becoming ill,

state officials wanted to measure MTBE or its by-products in blood from

samples of individuals with and without symptoms to determine whether

MTBE exposure might be the cause or a contributing factor. Objective

measures of individual exposure might have allowed public health officials

to conclusively demonstrate or rule out a link between the outbreak and

exposure, something that was not possible with environmental data and

epidemiologic surveys. The chemicals officials most often cited as wanting

to study using human exposure data but could not were pesticides and

volatile organic compounds.

Significant Information

and Infrastructure

Gaps Point to Need for

Strategic Planning and

Coordination

As part of our survey and interviews, we asked public health experts and

state and federal officials to identify barriers they considered significant to

their efforts to collect and use human exposure data. Officials cited two

primary barriers: the lack of laboratory capacity or methods to analyze

tissue samples and the lack of information to help set exposure test results

in context. Addressing these barriers takes time and resources. In that

regard, we identified a third barrier to more effective use of existing

resources: HHS and EPA lack a long-term strategic plan to address

infrastructure and science barriers, coordinate efforts to meet federal and

state needs, and address the many questions about how to set priorities

given their limited resources.
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Laboratory Capacity and

Methods to Measure More

Chemicals Needed

State officials frequently said insufficient laboratory capacity in their states

and at the federal level hindered their ability to obtain human exposure

data in cases where they thought such data were important. Over half of

the officials said their states lacked sufficient numbers of trained

laboratory staff, sufficient laboratory capacity to analyze samples, or

sufficient laboratory equipment. Many officials attribute such capacity

limitations to funding constraints because tissue analyses can be timeconsuming and expensive to perform. For example, according to a CDC

official, each test to measure dioxins in a sample requires (1) a laboratory

free from chemicals that could compromise test results, (2) specialized

equipment that costs about $500,000, and (3) highly trained and

experienced staff to complete. Officials of a professional organization

representing public health laboratories told us that, although many state

laboratories perceive they have a role in conducting tests to detect toxic

substances in humans, very few currently have such capacity.29

State and federal officials we interviewed told us that because few state

laboratories have the necessary equipment and expertise, they often rely

on CDC’s environmental health laboratory staff to analyze tissue samples.

Given the specialized laboratory requirements, CDC’s environmental health

laboratory is generally considered the best-suited to analyze tissue samples

for a range of chemicals and has, in fact, developed many of the methods to

do so, according to federal and state officials. CDC’s laboratory performs

measurements for most federal and many state efforts to gather human

exposure data. Many officials said CDC’s laboratory capacity is essential to

their efforts and needs to expand to meet growing needs. A few state

officials said CDC’s laboratory consistently returned test results when

people’s lives were at risk but was less able to help states assess health

risks more generally. An official in one state said that, while CDC’s

assistance is invaluable, the state’s laboratory capacity allowed public

health officials to obtain human exposure data and investigate citizen’s

concerns more frequently than they could if they had to rely soley on CDC’s

laboratory capacity.

29This organization actively supports expanding state and local laboratory capacity to

participate in a human biomonitoring program to provide human exposure data that would

enhance the effectiveness of environmental policy and regulatory decisions. In addition, this

group helped states apply for the four grants CDC offered to increase state and local

laboratory capacity to detect in human fluids and tissues chemicals that could be used in a

terrorist attack. Illustrating their interest in developing such laboratory capacity, 31 state

and 2 local health departments applied for the four grants.
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Another significant issue is the lack of analytical laboratory methods to

measure chemicals of concern. Despite advances over the past 2 decades in

analytic chemistry and molecular biology, laboratory methods have not

been developed to measure about 88 percent of the 1,456 chemicals in our

review, according to information provided by CDC and EPA officials.

Although laboratory staff at CDC have quickly applied scientific and

technological advances to develop new and more efficient laboratory

methods, they are concerned about the lack of methods to test a single

human sample for several related toxics. For example, a method exists to

measure arsenic in blood but not to measure arsenic and other heavy

metals at the same time. Such methods make more efficient use of the

samples that are gathered and greatly reduce the time and money needed to

test large numbers of samples. While CDC’s laboratory continuously

develops new chemical testing methods, current resources limit the

number to about 10 annually.

Even when analytical methods exist, efforts to gather human exposure data

are sometimes limited by problems with the methods used to gather the

samples. This is especially true for young children, a group thought to be

particularly susceptible to harmful effects from exposure. In some cases,

existing laboratory methods require sample volumes that can only be

obtained through invasive techniques. That is, blood samples must be

obtained by puncturing a vein rather than by pricking a finger. Many people

will not allow their children to participate in studies that require such

techniques. Similarly, urine samples can be difficult to obtain from children

who wear diapers. For example, substances in the diapers can compromise

test results.

Information Needed to

Interpret Human Exposure

Measurements

To help interpret the results of laboratory analysis and determine what

actions, if any, are needed to protect the public’s health, state and federal

officials cited the need for two types of context-setting data: comparative

(or reference range) information that shows exposure levels among the

general population and research that links exposure to adverse health

effects. At the state level, where many of the specific actions regarding atrisk situations are taken, almost three-fourths of responding officials cited

the lack of such information as a problem.

State officials said that reference range data, when available, allowed them

to determine whether exposures are sufficiently high to merit action to

reduce or prevent further exposure. For example, in one state, public

health officials, with help from CDC, responded to citizens’ reports of foul
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odors from leaking tanks at a waste cleanup site by gathering and analyzing

blood samples from those living nearby. CDC’s analysis of the blood

samples showed that residents near the site had exposure levels at the high

end of a CDC-developed reference range. State and federal officials

ordered the contractor to move the cleanup operations to another location.

Over 60 percent of state officials responding to our survey said the lack of

reference range data prevented them from using human exposure data in

their work. State officials said the problem for research about adverse

health effects was similar. Much of the data linking exposure to health

effects concerns high-level occupational exposures or higher doses

administered to laboratory animals. Consequently, translating the results of

such research to lower-level exposures of people and determining how best

to advise people about potential effects is problematic.

Federal health officials and researchers also cited a need for both types of

information in their investigations, particularly for federally supported

work in specific geographic areas. ATSDR officials said the lack of

reference ranges was a particular reason they could not generate human

exposure data more often in public health assessments and exposure

investigations. When data allow officials to put exposure into context,

concerns can be investigated and addressed. For example, in one

community, where citizens were concerned about exposure to dioxins from

nearby chemical manufacturing plants, ATSDR officials had CDC’s

laboratory analyze blood samples and found that some residents had levels

of several dioxins above the highest levels in a CDC-ATSDR-developed

reference range. In response, ATSDR helped residents obtain assistance

from medical professionals expert in dioxins and, working with state and

federal environmental agencies, began environmental testing to locate the

exposure source.

Stronger Interagency

Efforts Needed for Strategic

Planning and Coordination

The barriers outlined above present daunting challenges to state and

federal agencies. The number of chemicals that remain to be investigated

and the kinds of information needed are substantial, the research is often

expensive, and progress is often slow. At the same time, the level of

resources available for dealing with the issue is limited, and responsibilities

are fragmented among many state and federal agencies. Many studies have

pointed to the need for better coordination. While HHS and EPA efforts

have been coordinated through, for example, participation on advisory

committees and the use of CDC’s laboratory for performing the actual

measurements, such coordination falls short of what is needed for longterm planning. This need is illustrated by the growing convergence of
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interest in the planned expansions of NHANES and NHEXAS. To ensure as

much progress as possible with available resources, HHS and EPA need a

strategic planning effort that reflects a clear set of priorities, a framework

for coordinating data collection and reporting efforts, and a tie to

performance goals.

Agreement About Need for

Better Planning and

Coordination of Efforts Is

Widespread

In 1991, NRC reported that “although a successful monitoring program

must be highly relevant to regulatory needs, it could and should serve a

wide range of client programs and must not be dominated by any one of

them.” NRC reported that the approaches of EPA, CDC, and ATSDR are

each important in the identification and control of environmental hazards

to human health and that coordination among the programs would enhance

federal monitoring efforts and benefit researchers, health professionals,

and the public.30

Officials and experts agree that interagency interaction is needed to take

advantage of all approaches and information available to develop the most

cost-effective, least burdensome approach for collecting needed exposure

data. Towards this end, HHS agencies and EPA have at various times

attempted to collaborate in their respective exposure monitoring efforts.

For example, EPA solicited broad interagency input into the design of

NHEXAS and established interagency agreements with CDC and others to

assist in performing laboratory measurements, quality control, and other

support functions. Also through interagency agreements, CDC has

broadened the exposure monitoring component of NHANES to incorporate

the needs of EPA researchers.

30While NRC found EPA in the best position to house a human exposure monitoring

program, it also found that the ambivalence within EPA about the National Human

Monitoring program’s future indicated that the match of program goals, potential benefits,

and EPA mandates was not perfect.
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Outside reviews and involved researchers and officials indicate that even

with recent efforts, coordination has fallen short in ensuring adequate

interaction and linkages between agencies. For example, EPA’s scientific

advisers reviewed the NHEXAS pilot surveys and concluded that, while

NHEXAS was an excellent project and highly relevant for providing needed

information, a strategic plan was needed for follow-up studies. They also

urged that EPA link NHEXAS exposure data with biological data from

NHANES, where possible, and develop a more collaborative process for

gathering input for chemical selection. Attendees at a September 1999

NIEHS conference on the Role of Human Exposure Assessment in the

Prevention of Environmental Disease also called for a coordinated

interagency effort in assessing human exposure.31 One theme and

recommendation from the discussions was the need to bridge scientific

disciplines and agency missions to address knowledge gaps in assessing

human exposure.

State officials and others have also indicated that better linkages and

partnering are needed between federal, state, and local agencies. For

example, an official of the Association of Public Health Laboratories told

us that one way to improve states’ involvement in a national exposure

monitoring program would be to further their capability to assess levels of

toxic chemicals in their own populations relative to national levels. This

would require, in this official’s view, the transfer of new monitoring

technology to state public health laboratories, along with the resources

necessary to support that technology. Improved capacity at the state level

would allow federal laboratories to concentrate on developing more and

faster analytical methods for measuring chemicals in tissues and on

responding to crisis situations. Other experts have also called for better

linkages between federal efforts and communities and community

concerns. For example, the NHEXAS reviewers recommended that EPA

improve communication between NHEXAS investigators and state and

local health officials. Another theme of the conference on human exposure

assessment was that efforts to assess human exposure be in line with

public health goals and community concerns.

31The NIEHS-supported conference addressed many opportunities and challenges in

exposure assessment research, including exposure-analysis methodology, exposure-disease

relationships, regulatory and legislative issues, gene-environment interactions, disease

prevention and intervention, and some current federal initiatives related to exposure

assessment. One area of discussion was the need for and limitations of biological measures

of exposure.
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Individual Priorities

Contribute to Difficulties in

Coordinating Efforts

The challenges federal and state agencies face in setting priorities for

which chemicals to assess in their individual programs likely contribute to

the difficulties they have in collaborating with one another. The expense of

conducting exposure measurements in ongoing surveys—especially for the

number of samples required to establish national or regional trends and

levels—necessitates that priorities be set. However, agreeing on

priorities—or even agreeing on the process for setting priorities—is

challenging and resource-intensive. For example, to identify chemicals to

measure in NHEXAS, EPA undertook an extensive selection process,

soliciting input from regional and program offices.32 EPA’s scientific

advisers, while supportive of the program, cited the criteria for selecting

target chemicals as a weakness. NHANES is even less formal in this regard,

with no documented priority-setting process for chemicals to be measured.

Chemicals measured are largely determined by CDC’s laboratory scientists

based on such factors as the availability of analytical methods for

measuring the chemical and the laboratory’s capacity to perform the

measurements.33 According to a CDC official, CDC’s limited staff and

laboratory resources cannot develop the administrative infrastructure to

establish a scientific review process for selecting priority chemicals.

Another challenge in setting priorities, according to some officials, is the

appropriate balance between gathering exposure information on chemicals

about which little is known and gathering information on those already

considered to be toxic. NHANES and NHEXAS, for example, focus largely

on chemicals that are considered to be toxic at some level. By contrast, the

National Toxicology Program’s Human Exposure Initiative is intended to

help set priorities for chemical toxicological testing and might gather

baseline information on chemicals and chemical mixtures occurring in the

population that are not necessarily already known as harmful.

32Because of its emphasis on evaluating total human exposure, NHEXAS emphasized those

chemicals that can be measured in multiple environmental media (for example in air, water,

and food) as well as human tissues.

33CDC’s laboratory officials indicated that their choice of chemicals is determined by the

availability of high-quality analytical methods with adequate throughput, whether the

chemical is a known or suspected cause of health problems, whether the chemical is on EPA

and ATSDR priority lists, the number of persons likely exposed, and the availability of

funding from collaborators.
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Officials we interviewed raised many other concerns that would need to be

addressed when trying to coordinate efforts among multiple federal and

state agencies and programs:

• For what specific purpose(s) will these data be collected?

• What chemicals should be measured, in what order, how frequently, and

in what specific tissues?34

• What chemicals should be measured concurrently with or only through

personal environmental measurements?

• What is the best way to identify populations that might be at higher risk

of exposure?

• What chemicals should be monitored in humans nationally, versus

regionally or locally?35

• How can exposure data be coupled with our increasing knowledge

about the effect genetic factors have on risk from exposure to improve

the understanding about an individual’s risk from chemical

contaminants?

• What role should state agencies have in conducting human exposure

measurements and in planning federal efforts?

The fragmentation of responsibilities and efforts for assessing human

exposure reflect larger issues in the fragmentation of responsibility for

environmental health. For over a decade, a number of studies have pointed

34Several officials pointed to the importance of developing a breast milk monitoring

program. Many environmental agents are fat soluble and are released into breast milk at

significant concentrations. Examples include dioxins and PCBs. According to NIEHS

researchers, 6 months of nursing could result in dioxin or PCB concentrations in infants

which are 10 times higher than in the mother. Breast milk monitoring programs operate in

several European countries including Sweden, Germany, and the Netherlands.

35EPA’s scientific advisers’ review of the NHEXAS pilot surveys illustrates some of the tradeoffs in determining the appropriate balance between large population surveys and more

targeted follow-up surveys. The advisers reported that population studies are the only

means for collecting baseline information for such uses as trend analysis. NHANES is an

example of such a probability study. On the other hand, more targeted special studies tend

to assess high-end exposure groups more precisely. Additionally, the review illustrated how

total exposure data may be unnecessary to collect for chemicals at a national level,

depending on the chemical. The advisers pointed out that targeted special studies can be

used to identify sources and factors associated with high-end exposures. While

identification of major sources, media, and pathways for populations experiencing high

exposures are essential to reduce unacceptably high risks, if the majority of the national

population is exposed to pollutants at levels under health-related benchmarks, source

identification for such exposures is not a priority from a health standpoint.
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to the need for improved coordination between regulatory and health

agencies (see table 4).

Table 4: Examples of Reports Calling for Coordination in Environmental Health

Potential for Convergence of

Effort Is Increasing

The importance of planning and coordination is magnified by the possible

overlap in current plans to expand human exposure monitoring efforts.

This potential can be seen in HHS’ and EPA’s plans for NHANES and

proposed expansions of the NHEXAS pilots. Although nearly two-thirds of

the chemicals measured in the NHEXAS pilot surveys are currently

measured or planned for NHANES, the two efforts have taken differing

approaches in the past to monitoring the population’s exposure to these

chemicals.36 The NHEXAS pilots have focused on “total” exposure, which

entailed measurements in human tissues, water, air, food, dust, and other

potential sources in participants’ living environments, and data-gathering

has focused on three selected regions of the country. Total exposure

Report Description

Environmental Health Data Needs: An Action

Plan for Federal Public Health Agencies

(Public Health Foundation, 1997)

Called for the federal government to facilitate stronger ties between environmental

protection and public health agencies, perhaps by strengthening organizational links and

coordinating funding for federal (EPA and HHS) programs. Also indicated that priority

environmental health information needs included more complete exposure data, including

laboratory data such as biological measurements.

Burke, Shalauta, and Tran, The

Environmental Web: Impact of Federal

Statutes on State Environmental Health and

Protection (Public Health Service, Jan. 1995)

Found that progress in understanding the relationship between human health and the

environment will require, among other actions, improved cooperation between the many

health and environmental agencies at the federal, state, and local levels.

Researching Health Risks (Office of

Technology Assessment, 1993)

Reported that although agencies are expanding their research efforts, few incentives exist

for them to collaborate, and the lack of collaboration can only hinder progress in applying

newly developed techniques and knowledge to understanding the potential links between

exposure and adverse health effects.

The Potential for Linking Environmental and

Health Data (National Governors’

Association, 1990)

Reported that linkage of environmental and health data to investigate possible

connections between exposure and adverse health effects cannot occur without

interagency communication and cooperation, which rarely evolves naturally.

The Future of Public Health (Institute of

Medicine, 1988)

Found that separating environmental health from public health programs impeded

desirable coordination and could limit the depth of analyses given to the health

implications of environmental hazards.

36The follow-up to the NHEXAS pilots has not been planned, so the identity of the chemicals

to be measured is not known.
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measurements can help identify those sources that most contribute to

exposure—a critical part of determining how to take action to reduce or

prevent exposures. However, measuring total exposure requires several

types of laboratory measurements and is thus more expensive. By contrast,

NHANES has focused its exposure monitoring on human biological

measurements and on a sample that is generally representative of the

nation as a whole. Biological monitoring data demonstrate exposure from

all sources, but determining exposure sources usually requires additional

environmental measurements. Other than the few chemicals it covered,

NHANES has historically been considered an awkward vehicle for

including exposure monitoring—in large part because of its wide range of

competing goals and lack of a primary commitment to monitoring tissues

for exposures.

Changes to the 1999 NHANES, such as the following, show a greater

emphasis in environmental health. These changes along with EPA’s plans to

expand NHEXAS suggest a convergence of the two approaches and a

growing and overlapping interest among agencies in exposure

measurement and monitoring.

• NHANES now has a goal of monitoring exposures. Starting with

NHANES 1999, CDC formalized its commitment to monitoring trends in

the nation’s environmental exposures by establishing this as a stated

goal of NHANES.37 In line with this goal, CDC’s laboratory plans to issue

37At this writing, NHANES’ goals are to (1) estimate the number and percentage of persons

in the United States and designated subgroups with selected diseases and risk factors; (2)

monitor trends in the prevalence, awareness, treatment, and control of selected diseases;

(3) monitor trends in risk behaviors and environmental exposures; (4) analyze risk factors

for selected diseases; (5) study the relationship between diet, nutrition, and health; (6)

explore emerging public health issues and new technologies; and (7) establish a national

probability sample of genetic material for future genetic research. CDC officials told us that

the emerging focus in NHANES on environmental health issues reflects advances in

technology as well as the public’s increasing priority for understanding the impacts of

environment on health. Part of CDC’s responsibility is to report on environmental hazards

and determinants of health. Section 306 of the Public Health Service Act (42 U.S. C. 242k)

directs the National Center for Health Statistics, the CDC agency that conducts NHANES, to

collect statistics on subjects such as the extent and nature of illness and disability of the

population; environmental, social, and other health hazards; determinants of health; health

resources; and utilization of health care.
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this year a “National Exposure Report Card” using NHANES samples.38

This goal is similar to EPA’s goal as proposed for NHEXAS’ follow-up

survey—to document the status and trends of the national distributions

of human exposure to potentially high-risk chemicals.

• NHANES will include selected environmental measurements. Starting

with NHANES 1999, environmental measurements, such as contaminant

levels in water and house dust, and levels measured through personal air

monitors worn by participants will be included in the survey to help

identify potential sources of exposure.39

• NHANES will be conducted continuously rather than periodically,

allowing for more flexibility in the measurements it includes. According

to CDC officials, the new annual sampling design will enable them to

include emerging and changing priorities in the data collected through

the survey and thus allow for a broader collection of data than in

previous surveys, including exposure and measurements in people’s

personal environments.

Other planned changes to NHANES and NHEXAS also indicate a growing

overlap in approaches and interests. For example, pending analysis and

evaluation of its pilot surveys, EPA is proposing to expand NHEXAS

beyond the regional focus of its pilot to include a nationally representative

sample similar to the framework of NHANES. Also, both CDC and EPA

would like to eventually include a component in NHANES and NHEXAS to

monitor special populations. EPA’s proposed expansion of NHEXAS would

eventually include “special studies” to examine high-end exposures in more

detail and with greater precision. Small populations for further study would

be identified through the national survey. CDC also plans to add a

component to NHANES that will gather selected NHANES health and

nutrition data, possibly including exposure measurements, on specific

subpopulations in geographic areas of interest or among specific racial or

ethnic minority populations. This effort to add a subpopulation component

38According to CDC laboratory officials, the first report card will provide data on exposure

levels of the population to 25 chemicals that have not yet been determined. These might

include selected heavy metals, indoor air pollutants, nonpersistant pesticides, and

phthalates.

39Because of the wide range of other health and nutrition questions addressed in NHANES,

environmental measurements currently included are less extensive than those included in

NHEXAS because, for example, food and beverage samples are not conducted.
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to NHANES was initiated in response to the needs of state health officials

and others for local level data.

Funding Is Sporadic, and

Funding Priorities Change

Part of the difficulty in collaborating and in planning human exposure

monitoring efforts to meet longer-term needs may also arise from issues of

sporadic funding and resources to support these efforts. As compared to

the hundreds of millions spent on monitoring contaminants in

environmental media, we estimate that less than $7 million was spent

collectively by CDC (including ATSDR) and EPA on their respective human

exposure efforts in 1999.40

Neither CDC nor EPA has provided a dedicated funding stream for their

exposure measurement efforts. Funding for efforts has, to a large extent,

depended on priorities established year to year. For example, funding for

the exposure and other environmental components of NHANES depends to

some extent on the interests of other federal agencies and their willingness

to pay for related data gathering and analysis.41 CDC estimated it would

spend about $4.7 million for laboratory measurements and laboratory staff

costs in 1999 for NHANES-related exposure measurements such as lead,

mercury, cotinine, heavy metals, pesticides, volatile organic compounds,

and other chemical classes. Interagency agreements document the receipt

of about $1.2 million from collaborators for some of those laboratory

measurements. If other agencies do not pay CDC to conduct laboratory

tests—with the exception of some “core” measurements, such as lead—

CDC performs tests as time and laboratory resources allow. For example,

40NIEHS-CDC interagency agreements document that NIEHS had provided about $3.3

million to CDC between fiscal years 1996 and 2000 for performing environmental exposure

measurements for its Human Exposure Initiative. No funding was provided in fiscal year

1999.

41NHANES 1999, for example, received $15.9 million in appropriated funding and, according

to CDC officials, an additional $6.8 million from collaborating institutions. Interagency

agreements related to environmental measurements performed in conjunction with

NHANES document the receipt of about $1.4 million from collaborators at EPA and other

agencies for environmental exposure measurements. In addition to EPA’s support for

measurement of certain chemicals in human tissues, an estimated $125,000 was received

from the Department of Housing and Urban Development for performing dust sampling and

an estimated $30,000 from the Mickey Leland National Urban Air Toxics for personal

measurements of volatile organic compounds. CDC laboratory officials indicated that the

increase to their fiscal year 2000 funding for the environmental health laboratory has

improved their ability to support needed laboratory measurements for NHANES and other

efforts. This funding increased by about $5 million between fiscal years 1999 and 2000.
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although CDC initially proposed for the survey starting in 1999 to measure

up to 210 chemicals in tissues of a subset of NHANES survey participants,

CDC officials indicated that those chemicals could be measured only as

resources allowed.42 At the time of our review, a CDC laboratory official

indicated that resources might allow them to include about 74 chemicals in

1999 and 2000.

EPA’s commitment to funding NHEXAS also remains uncertain. EPA

officials estimated that approximately $20 million was spent on NHEXAS

from 1993 through 1999—with a decreasing amount designated to the

project in 1999 and 2000. While EPA’s independent scientific advisers

commended the design for NHEXAS and said it could be the basis for an

effective national program, they expressed concerns about the limited

resources allocated to analyze the data gathered in the pilot projects.43 At a

national level, EPA has dedicated approximately three full-time positions to

evaluate the data from the NHEXAS pilots and design future expansions.

Better Linkages to Program

Goals and Performance

Monitoring Needed

The Government Performance and Results Act of 1993 (Results Act)

provides federal agencies a structured framework to coordinate efforts in

crosscutting programs when agency missions overlap. The Results Act

requires federal agencies, as part of their mandated responsibilities, to

prepare annual performance plans that discuss agency goals and

performance measures. Past reviews have shown that EPA, HHS, and other

federal agencies have not fully used the Results Act planning process to

explain how each would coordinate crosscutting efforts with other

agencies. Few agency plans attempt the challenging task of discussing

planned strategies for coordination and establishing complementary

performance goals and common or complementary performance measures.

A major weakness of EPA’s fiscal year 2000 Annual Performance Plan was

the lack of sufficient detail describing crosscutting goals and activities or

how EPA planned to coordinate with other federal agencies on related

42According to CDC officials, uncertain funding may limit their ability to perform NHANES

measurements for dioxins, furans, coplanercoplanar PCBs, phytoestrogens, certain heavy

metals, phthalates, and polyaromatic hydrocarbons.

43EPA officials indicated that at the individual study level, approximately $250,000 was

allocated for analyses of the NHEXAS pilot data in fiscal year 1999; EPA plans to spend

approximately $170,000 in fiscal year 2000.
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strategic or performance goals.44 For example, under its plan’s “safe food”

objective, EPA discusses coordinating with HHS and other agencies to

reduce health risks from pesticides. However, it did not outline specific

projects and strategies, responsibilities, and products that must be

coordinated for EPA to accomplish its goals. Similarly, HHS’ performance

plan lacked details regarding how crosscutting activities and goals would

be coordinated with other agencies.

In their fiscal year 2001 performance plans, EPA and CDC make limited use

of human exposure data to measure or validate performance, and neither

agency describes how data collection efforts relate to complementary goals

of other federal agencies. For example, EPA and CDC have the common

goal of reducing childhood lead poisoning, but only CDC uses data on

blood lead levels to validate progress toward this goal. Although EPA has

goals that are clearly related to reducing human exposure to other toxic

chemicals, the human exposure data collected by EPA and CDC have

largely not been linked with or used to measure progress. Such data show

potential for helping elucidate federal progress in environmental efforts,

but EPA has not yet acted to fully realize such potential. For example,

NHEXAS data are used to help assess children’s exposure to pesticides.

However, a related goal to reduce public exposure to pesticides does not

use human exposure data; instead, it relies on the number of activities to

educate agricultural workers and the public. The effectiveness of these

efforts could be assessed, in part, through measured reductions in actual

human exposure to specific pesticides. During 1999, CDC maintained a goal

to develop methods to measure toxic substances in humans and added a

goal to measure and report on human exposure to toxic substances.

However, neither goal discusses how CDC will coordinate with EPA and

other federal programs in meeting these goals and ensuring that newly

developed methods and measured substances meet priority data needs.

Successful Models for Planning

and Coordination Point to the

Need for High-Level Mandate,

Process for Inclusion, and

Mechanism for Reporting

Program officials at HHS and EPA told us in early 2000 that they were

discussing the merits of establishing a new interagency program in human

44See Observations on the Environmental Protection Agency’s Fiscal Year 2000 Performance

Plan (GAO/RCED-99-237R) July 20, 1999.
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exposure monitoring.45 At the time of our review, the proposal was in early

stages of discussion and officials had not clarified how a new program

would consider states’ information needs, differ from or relate to NHANES

and the NHEXAS pilot surveys, or resolve past issues about differing

agency goals and priorities.

Several experts and agency officials have pointed to successful models of

interagency collaboration in environmental health issues that could help

shape an HHS-EPA interagency effort. One such model is the collaboration

on children’s environmental health issues. In this case, Executive Order

13045, signed by the President on April 21, 1997, established a Task Force

on Environmental Health Risks and Safety Risks to Children to develop and

recommend federal strategies for children’s environmental health and

safety. Among the elements that have been cited as contributing to success

were a clear mandate to collaborate and a process to respond to the input

and data needs of different stakeholders. According to involved officials, a

high-level interagency work group has worked closely to address its

charges. These charges include developing general policy and annual

priorities; a coordinated federal research agenda; recommendations for

partnerships among federal, state, local, and tribal governments and the

private, academic, and nonprofit sectors; and identifying high-priority

initiatives to advance protection of children’s environmental health.46

A second model with a top-down mandate and a process to respond to

stakeholders is NTP, established in 1978 as an HHS-wide effort to provide

regulatory and research agencies needed information about potentially

toxic and hazardous chemicals nationwide and to strengthen the science

base in toxicology. According to officials, part of NTP’s success in fostering

collaboration are an inclusive executive committee and an established

process for decisionmaking. The NTP Executive Committee, which

provides policy oversight of NTP, includes agencies outside of HHS, such as

EPA and the Consumer Product Safety Commission. The NTP Executive

Committee also serves as a decisionmaking body, in that members cast

votes on key issues, such as prioritization of chemicals for study and for

45This effort was coordinated through the White House Office of Science and Technology

Policy.

46Executive Order 13045 also indicates such strategies are to include proposals to enhance

public outreach and communication and a statement regarding the desirability of new

legislation to fulfill or promote the purposes of the order.
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listing in NTP’s Report on Carcinogens.47 Involved officials believe the

voting requirement helps move key issues forward and provides an

effective means of resolving disagreements. NTP also has an inclusive

process for identifying chemicals to be considered by the Executive

Committee. NTP’s chemical testing nominations are solicited from sources

in academia, federal and state regulatory and health agencies, industry, and

unions, as well as environmental groups and the general public.

Several officials indicated that reports on exposures in the national

population to toxic chemicals are needed to help inform policymakers,

researchers, and the public. Specifically, such reports can help identify

serious human health risks, help officials link exposures to sources,

determine appropriate interventions to help reduce these risks, and

document the effectiveness of interventions in reducing exposures.

Moreover, agencies could use such reports to validate or measure progress

in meeting goals established under the Results Act. A key element of NTP is

its biennial reports. As informational scientific and public health

documents, these reports are not only used by federal and state agencies

but are considered an important medium for informing the public and

policymakers on the status of substances considered likely to be

carcinogenic for humans.

Conclusions The nation has a long way to go in measuring human exposures to

potentially harmful chemicals. While federal efforts are increasingly

covering chemicals of potential concern, there are substantial gaps in

current information on exposure levels, the health risks that result, and

those who may be most at risk. Recent advances in laboratory technology

show promise for improving the collection and analysis of some of the

information needed to understand and measure human exposures.

However, a more long-term and concerted effort to address infrastructure

and scientific limitations in measuring exposure will be required if

substantive progress is to be made. Applying and continually improving

47The Director of NTP issues the Report on Carcinogens pursuant to a 1978 amendment,

section 301(B)(4) of the Public Health Services Act, which requires the Secretary of HHS to

publish a list of all substances that are either known to be human carcinogens or may

reasonably be anticipated to be human carcinogens and to which a significant number of

persons residing in the United States are exposed. NTP issues a revised Report on

Carcinogens every 2 years.
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upon these advances to cover an increasing number of chemicals and

issues will require both time and resources. CDC’s laboratory to date has

been able to meet many demands for human exposure data for federal and

state measurement and monitoring efforts. However, its capacity, given

current resources, will continue to limit progress to develop new methods

and include more people and chemicals in federal and state efforts.

Federal agencies are currently planning whether and how they can expand

existing programs to meet the significant needs for human exposure data.

Collaboration in such planning is essential, because agencies have different

capacities and skills, and separate attempts have fallen short of supporting

the large efforts that are needed. So far, no clear strategy has emerged for

how to carry out this major task, particularly given the growing and

overlapping interests among many agencies for understanding and

measuring human exposures to potentially harmful chemicals. In our view,

developing such a strategy is a challenging but necessary first step.

In the meantime, state and local health officials must try to understand and

communicate the risks from environmental contaminants to concerned

citizens—a difficult, if not impossible, task when information is unavailable

to help them interpret the risks from the exposures citizens face in their

daily environments. State officials indicate they need more of the

information that is collected through federal efforts to help interpret those

levels faced by citizens in their states. And to collect measurements for

their studies and investigations, state officials are faced with finding

laboratories that have the equipment and capacity to perform the complex

measurements. Federal capacity, largely centered at CDC, cannot meet

states’ needs in many situations, and laboratory capacity is lacking in most

states.

To help meet the gaps in environmental exposure data at all levels of

government, EPA and the various HHS agencies with environmental health

responsibilities need to work closely together to forge a strategic plan

laying out the necessary next steps for addressing human exposure

information and concerns. In addition to considering states’ needs and

capacities for collecting human exposure data, such a plan could

• provide long-term structure to human exposure monitoring as an

interagency effort,

• establish a mechanism for setting program priorities in line with agency

goals and performance measures,

• clarify agency roles and minimize duplication, and
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• help agencies share expertise.

Policymakers, agencies, and the public seek many types of information on

exposure trends and levels in the national population as well as for groups

considered potentially at risk of disproportionate exposures. Resolution is

also needed on what information should be reported on national trends and

levels of exposure. A strategic plan could help agencies resolve the many

different informational needs to determine what exposure information

should be reported and how agencies can work together to report such

information.

Recommendations to

the Secretary of HHS

and the Administrator

of EPA

We recommend that the Secretary of HHS and the Administrator of EPA

develop a coordinated federal strategy for the short- and long-term

monitoring of human exposures to potentially toxic chemicals. In

developing such a strategy, the Secretary and the Administrator should

assess the need for an interagency program to collect and report data on

human exposures, the extent current surveys and agency efforts can be

used as part of such an effort, and the funding needs and sources to sustain

a viable program for monitoring human exposures to toxic substances.

Such a strategy should

• address individual agency needs and expertise,

• provide a framework for coordinating efforts to gather data needed to

improve understanding of human exposures,

• assess needed federal and state laboratory capacity,

• establish research priorities for laboratory methods development and a

mechanism or process for setting chemical monitoring priorities,

• develop a framework for identifying at-risk populations, and

• consider states’ informational needs.

We further recommend that the agencies identify common or

complementary performance goals or measures to reduce, monitor, or

develop methods for measuring human exposures to toxic chemicals. Such

goals or measures can be a basis for structuring and supporting interagency

collaborations to collect and use human exposure data.

As part of this coordinated strategy, we recommend that the Secretary of

HHS and Administrator of EPA periodically publish a report on levels and

trends in the national population of exposures to selected toxic substances.
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Agency Comments We provided HHS and EPA an opportunity to comment on a draft of this

report. Both agencies generally concurred with our conclusions and

recommendations—that a long-term coordinated federal strategy was

needed for monitoring human exposures to potentially toxic chemicals and

that such efforts could be linked through common or complementary

performance goals—and indicated that they would work together to

implement our recommendations. (See apps. IV and V, respectively.) HHS

and EPA also both stressed the importance, as discussed in our report, of

expanding the scope of their efforts to monitor and measure human

exposures to toxic chemicals beyond the limited number of chemicals

covered today. To support such expansions, HHS noted the importance of

additional resources for improving laboratory capacity and methods.

HHS and EPA provided several other comments raising points that one or

both agencies consider important to monitoring human exposures to toxic

chemicals. These included the need to (1) coordinate any exposure

monitoring in the general population with monitoring of occupational

exposures; (2) consider adding the monitoring of breast milk in a national

program; (3) depending on the chemical and the purpose for the data

collection, consider measures of human exposure other than the

concentration in human tissues for collection; and (4) consider the option

of expanding the scope of NHANES as a means of improving data needed

to identify potentially at-risk subgroups. We agree that the points raised in

these comments are important and that they should be considered during

development of any coordinated federal strategy.

EPA also said that additional federal partners, including the Departments

of Defense, Transportation, and Energy should participate in developing

and supporting a coordinated federal strategy. We agree that it would be

appropriate to obtain input from all involved and interested agencies. HHS

and EPA also provided a number of clarifying and technical comments,

which we incorporated where appropriate.

We are sending copies of this report to the Honorable Donna E. Shalala,

Secretary of HHS, and the Honorable Carol M. Browner, Administrator,

EPA. We are also sending copies to Jeffrey P. Koplan, Director, CDC, and

Administrator, ATSDR; Ruth Kirschstein, Acting Director, NIH; Kenneth

Olden, Director, NIEHS; Richard J. Jackson, Director, National Center for

Environmental Health; Edward J. Sondik, National Center for Health

Statistics; Norine Noonan, Assistant Administrator for Research and
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Development, EPA; and other interested parties. We will make copies

available to others upon request.

If you or your staff have any questions, please contact me at (202) 512-7119.

Other major contributors are included in appendix VI.

Janet Heinrich

Associate Director, Health Financing

and Public Health Issues
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List of Requesters

The Honorable Nancy Pelosi

House of Representatives

The Honorable Maxine Waters

House of Representatives

The Honorable Eleanor Holmes Norton

House of Representatives

The Honorable Patsy Mink

House of Representatives

The Honorable Anne G. Eshoo

House of Representatives

The Honorable Nydia Velazquez

House of Representatives

The Honorable John Conyers

House of Representatives

The Honorable Louise Slaughter

House of Representatives

The Honorable Henry A. Waxman

House of Representatives
Page 45 GAO/HEHS-00-80 Environmental Health Data Needs
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Appendix I

Objectives, Scope, and Methodology ApApenednxidexiIs

Nine members of the Congress asked us to study the nation’s data collected

to assess human exposure to potentially toxic chemicals in the

environment. As agreed with our requesters, we focused our work

primarily on efforts to measure chemical exposures in human tissue

samples, such as blood, hair, and urine. This report discusses (1) the extent

to which state and federal agencies—specifically, HHS and EPA—collect

human exposure data on potentially harmful chemicals, including data to

identify at-risk populations, and (2) the main barriers hindering further

progress in such efforts.

Scope of Our Review Although laboratory measurements of chemical exposure are only one part

of the data collected to address environmental health concerns, they merit

attention because new technology makes it increasingly easy to measure

the degree to which a chemical has been absorbed into human tissues.

Such measurements are often a more accurate and useful approach to

assessing exposure than environmental measurements, according to public

health experts.

Because federal agencies that collect human exposure data collect these

data for different purposes, we were not able to assess the overall

adequacy of the nation’s efforts to address environmental health concerns.

Therefore, we focused our work at the federal level on the efforts of two

agencies—HHS and EPA—and the subcomponents of these agencies

involved in exposure measurement and monitoring in the U.S. population:

• EPA’s Office of Research and Development,

• HHS’ National Center for Environmental Health (NCEH),

• HHS’ National Center for Health Statistics (NCHS),

• HHS’ Agency for Toxic Substances and Disease Registry (ATSDR), and

• HHS’ National Institute of Environmental Health Sciences (NIEHS).

We focused our work mainly on nonoccupational environmental exposure

to chemical agents known or thought to pose a health hazard by one or

more of these agencies.

To gather information about activities of state officials, we surveyed

environmental health officials in state public health agencies and

conducted site visits to six states.
Appendix I

Objectives, Scope, and Methodology

Page 47 GAO/HEHS-00-80 Environmental Health Data Needs

Methodology of Our

Review

To assess the extent to which the federal agencies we reviewed have

collected human exposure data, we met with key officials responsible for

efforts intended to collect human exposure data at each agency. We

focused on what we identified as being the most significant federal efforts

in human exposure assessment at EPA and HHS related to nonoccupational

human exposure to environmental contaminants. We reviewed four major

activities: EPA’s National Human Exposure Assessment Survey (NHEXAS),

CDC’s National Health and Nutrition Examination Survey (NHANES),

NIEHS’ Human Exposure Initiative, and ATSDR’s exposure investigation

activities around hazardous waste and other sites. We also obtained

information on EPA’s National Human Adipose Tissue Survey (NHATS),

which ended in 1992.

We also interviewed officials and obtained documentation on how these

various programs were planned and organized and to assess the extent data

were collected in a manner that allows the identification of at-risk

subpopulations by such factors as income, race and ethnicity, age, and

geographic location. We obtained relevant budget information for 1999 and

reviewed related agency performance plans.

To assess barriers to progress in collecting or using human exposure data,

we interviewed federal officials involved in such efforts about past and

current views on such barriers. In addition, we reviewed the general

literature on human exposure to environmental chemicals and interviewed

officials from organizations representing state epidemiologists, state public

health laboratory directors, local public health officials, the chemical

industry, environmental advocates, and public health experts.

To gather nationwide data on the views of state public health officials, we

surveyed officials with environmental health responsibilities related to

chemical exposure in state public health agencies. We identified 93 officials

in each of the 50 states and the District of Columbia—referred to

collectively as states—with assistance from the Council of State and

Territorial Epidemiologists and officials in each of the 51 states.

We also conducted on-site work at EPA, CDC agencies, and NIEHS and in

six states—California, Louisiana, Massachusetts, North Carolina, Oregon,

and Washington. These six states were selected to represent diverse

geographic areas and environmental health programs. In the six states, we

interviewed state public health officials. We also interviewed officials in

state environmental protection and agriculture agencies, academic and
Appendix I

Objectives, Scope, and Methodology

Page 48 GAO/HEHS-00-80 Environmental Health Data Needs

independent researchers, and representatives of community advocacy

organizations.

We excluded efforts to collect human exposure data within occupational

settings from the scope of our review. Similarly, we excluded federally

supported academic and private sector research efforts.

Our work was conducted from March 1999 through March 2000 in

accordance with generally accepted government auditing standards.

Methodology for Chemical

List Analyses

To assess the extent to which human exposure data are available for

chemicals of high concern to human health, we analyzed a number of

chemical lists maintained by HHS and EPA agencies. We also identified

chemicals measured through HHS and EPA representative surveys.

Chemical data were gathered from various sources, including EPA’s Offices

of Pesticide Programs, Air and Radiation, Pollution Prevention and Toxics,

and Research and Development; the National Toxicology Program (NTP)

headquartered at NIEHS; CDC’s ATSDR; and NCEH and NCHS within

ATSDR. Several toxic chemical lists were identified through a review of

related reports and literature on environmental exposure issues. To narrow

the scope, we also contacted staff in relevant offices within these agencies

and asked them to identify key lists of chemicals of concern. We consulted

experts and public health laboratory officials at the Pew Commission for

Environmental Health and the Association for Public Health Laboratories.

From the many available chemical lists, we judgmentally selected eight

based on our assessment that each list contained chemicals thought to

have a high potential for causing harm to human health and input and

recommendations from experts. These eight lists, which contained more

than 1,400 unique chemicals, provide a conservative number of the

chemicals agency officials consider a concern for human health. To ensure

that chemicals with more than one name were not included more than

once, we used Chemical Abstract Service numbers, a unique identifier.

These lists, whether singly or combined, do not necessarily reflect the

highest priorities of the federal government or the agencies or programs we

contacted. The lists we reviewed are described below.

• Chemicals found most often at the nation’s Superfund sites: HHS’

ATSDR, which conducts public health assessments or other health

investigations for populations living around national priority hazardous
Appendix I

Objectives, Scope, and Methodology

Page 49 GAO/HEHS-00-80 Environmental Health Data Needs

waste sites, and EPA prepare a list, in order of priority, of hazardous

substances. This list contains substances that are most commonly found

at facilities on the National Priorities List (Superfund) and pose the

most significant potential threat to human health due to their known or

suspected toxicity and potential for human exposure.

• EPA’s list of toxics of concern in air: The Congress established the

original list of 188 hazardous air pollutants that EPA would regulate

through the Clean Air Act. EPA periodically must revise the list to add

or, when warranted, remove substances. EPA adds substances that it

determines to be air pollutants that are known to cause or may

reasonably be anticipated to cause adverse effects to human health or

adverse environmental effects.

• Chemicals harmful because of their persistence in the environment,

tendency to bioaccumulate in plant or animal tissues, and toxicity: EPA’s

Office of Solid Waste and Office of Pollution Prevention and Toxics

created this list of persistent, bioaccumulative, and toxic (PBT)

chemicals. PBT chemicals do not readily break down or decrease in

potency after they are released into the environment, even if released in

quantities that are very small and legally permitted. Over time, these

chemicals are likely to accumulate in soils or other environmental

media, be absorbed or ingested by animals and plants, accumulate in

animal and plant tissue, pass through the food chain, and potentially

cause long-term human health or ecological problems.

• Priority pesticides of potential concern: We combined two lists of

potentially harmful chemicals to develop this list. EPA’s Office of

Pesticides Programs provided a list of pesticides of concern that were

classified as organophosphates; carbamates; or group B1, B2, or C

carcinogens. According to a program official, these classes of pesticides

are generally considered among the most potentially harmful to human

health. We combined this list with the U.S. Department of Agriculture’s

Pesticide Data Program list of pesticides that are measured in selected

commodities or foods. Pesticides monitored by the program in 1997

included insecticides, herbicides, fungicides, and growth regulators in

fresh and processed fruit and vegetables, whole milk, and grains.

• Chemicals that are known or probable carcinogens: HHS’ Report on

Carcinogens includes substances known or reasonably thought to be

cancer-causing based on evaluations of substances performed by

scientists from NTP, other federal health research and regulatory

agencies, and nongovernment institutions. The list of substances in the

report represents an initial step in hazard identification. Substances

listed as “known to be human carcinogens” are those for which there is

sufficient evidence of carcinogenicity (cancer-causing potential) in
Appendix I

Objectives, Scope, and Methodology

Page 50 GAO/HEHS-00-80 Environmental Health Data Needs

humans to indicate a causal relationship between exposure to the agent,

substance, or mixture and human cancer. Substances listed as

“reasonably anticipated to be human carcinogens’’ are those for which

there is limited evidence of carcinogenicity in humans, insufficient

evidence of carcinogenicity in experimental animals, or both.

• Chemicals that are considered toxic and used, manufactured, treated,

transported, or released into the environment: EPA publishes the Toxics

Release Inventory containing information on the release and other

waste management activities of toxic chemicals by facilities that

manufacture, process, or otherwise use them. This database is made

available to the public and is considered useful to citizens, businesses,

and governments for purposes of working together to protect the quality

of their land, air, and water and for evaluating the probability that

chemical releases could impact human health in communities.

• Chemicals most in need of testing required by the Toxic Substances

Control Act: The Master Testing list contains those chemicals that are

prioritized for safety testing based on EPA’s finding that (1) a chemical

may present an unreasonable risk of injury to human health or the

environment and/or the chemical is produced in substantial quantities

that could result in significant or substantial human or environmental

exposure, (2) the available data to evaluate the chemical are inadequate,

and (3) testing is needed to develop the required data.

We compared the combined list of these chemicals, totaling 1,456, and each

individual list with those chemicals identified by EPA and CDC officials as

measured in the NHEXAS and NHANES human exposure efforts through

2000. We excluded NHATS’ and the Human Exposure Initiative’s chemical

lists from our analysis. NRC’s 1991 review of the NHATS program raised

questions about, for example, the representativeness of the results and the

methods used to handle the tissue specimens. NIEHS’ Human Exposure

Initiative measurements were not complete at the time of our review and

thus it was not known which chemicals had been or are currently being

measured.

Survey Development and

Distribution and Analysis

To develop survey questions, we reviewed documentation on

environmental health programs prepared by HHS and EPA agencies,

professional organizations representing state epidemiology and public

health laboratory officials, and public health experts. We also spoke with

officials and representatives from each of these groups.
Appendix I

Objectives, Scope, and Methodology

Page 51 GAO/HEHS-00-80 Environmental Health Data Needs

We pretested our survey in person with state environmental health officials

in two states and in teleconferences with officials in two additional states.

We asked knowledgeable people in EPA and CDC and in the environmental

and public health fields to review the survey instrument. We refined the

questionnaire in response to their comments to help ensure that potential

respondents could provide the information requested and that our

questions were fair, relevant, answerable with readily available

information, and relatively free of design flaws that could introduce bias or

error into our study results. We mailed questionnaires to the 93 officials in

August 1999. We sent at least one follow-up mailing and conducted

telephone follow-ups to nonrespondents. We ended data collection in

December 1999; had received responses from 81 officials in 48 states for a

response rate of 87 percent.

In preparing for our analysis, we reviewed and edited the completed

questionnaires and checked the data for consistency. We tested the validity

of the respondents’ answers and comments by comparing them with data

we gathered through interviews with public health experts and other public

health officials and with documentation obtained at federal agencies and in

case study states.

The survey and survey results are presented in appendix III.
Page 52 GAO/HEHS-00-80 Environmental Health Data Needs

Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts ApendxiI

Since the 1980s, reports reviewing environmental health data needs have

recommended the broader collection of human data showing actual human

exposures to chemical contaminants in the environment. Various federal

agencies have collected such human exposure data for a number of

purposes; historically, these collection efforts have been limited to selected

chemicals, subpopulations, and time periods.

Various Reports

Discuss the Gaps in

Human Data Showing

Measured Exposure to

Chemical

Contaminants

Data on actual levels of chemicals in humans has been a longstanding gap

in the information needed to establish human health risks from exposures

to environmental contaminants. While data on the concentration of

chemicals in environmental media—such as air, water, and food—have

historically been used to estimate human exposure to harmful chemicals,

this approach to detect or define human health risks has limitations.

According to the NRC, there are too many chemicals, too many sources,

and too many routes of exposure to rely solely on environmental

monitoring. Measurements of internal doses of exposure—actual levels of

chemicals or their metabolites found in human tissues, such as blood or

urine—are generally considered an accurate measure of human exposure.

Such measurements can reflect exposures from all routes and that may be

accumulated over time, modified by individual differences in physiology,

and difficult or impossible to assess by environmental measurements (such

as hand-to-mouth ingestion in young children). In 1991, NRC reported that

a program of human tissue monitoring is critical to the continued

improvement of understanding of exposure to toxic chemicals and

recommended that such a program be given high priority for funds and

other resources.1

Several other federal reviews have pointed to information needs in this

area. An interagency assessment of federally supported databases

conducted in the early 1990s concluded that federal data systems generally

lacked data on actual human exposures, including information about

contact between the chemical and the human body (personal exposures)

and the amount of the chemical absorbed (internal doses). The review also

found substantial value in collecting and analyzing these data in a

comprehensive and systematic manner and that the costs associated with

1

NRC, Commission on Life Sciences, Monitoring Human Tissues for Toxic Substances.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 53 GAO/HEHS-00-80 Environmental Health Data Needs

establishing and maintaining appropriate databases were justified.2 A

discussion of some of these reviews follow.

• HHS, NCHS, Environmental Health: A Plan for Collecting and

Coordinating Statistical and Epidemiologic Data (Washington, D.C.:

Government Printing Office, 1980): This report found that “acceptable

ranges of physiologic measurements and normal levels of trace

elements must be determined before any attempt can be made to

associate health outcomes with environmental exposures. Many of

these baseline data do not exist for particular populations of interest or

for specific pollutants. In addition, early indicators and symptoms of

disease that might be environmentally related are not clearly

understood.” The report identified a number of research directions to

help define the association between health effects and specific

environmental exposures, including the establishment of baseline data

on physiological measurements of trace elements in tissue and blood for

the population.

• HHS, NIEHS, Issues and Challenges in Environmental Health

(Washington, D.C.: National Institutes of Environmental Sciences, 1987):

This report found that due to “gaps in data systems established for

monitoring and surveillance of environmental exposure, effort should

be made to foster better linkage among existing systems. . . . Existing

data systems should be expanded to include biochemical and cellular

indicators of early stages of disease. . . . The group found there is a need

for more research and more systematic collection of data on the

exposure of human populations to harmful substances. Reliable

exposure data are necessary for assessing the probability that exposed

populations will develop adverse health effects and the likelihood of

success in intervening to reduce those risks.”

• K. Sexton and others, “Estimating Human Exposures to Environmental

Pollutants: Availability and Utility of Existing Databases”: This report

found that while “the evidence suggests that existing data systems

contain a substantial amount of information that is relevant to exposure

estimation . . . the quality of the data is inconsistent and difficult to

assess and that understanding and accessing the information is often

difficult. Furthermore, these systems demonstrate a striking absence of

data on actual human exposures, including a lack of information about

2

See K. Sexton and others, “Estimating Human Exposures to Environmental Pollutants:

Availability and Utility of Existing Databases,” Archives of Environmental Health, Vol. 47,

No. 6 (1992), pp. 398-407.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 54 GAO/HEHS-00-80 Environmental Health Data Needs

contact between the agent and the human body (exposure) and about

the amount of the agent or its metabolites that enters the body (dose).”

• NRC, Hormonally Active Agents in the Environment: This report found

that “determining the risk of environmental hormonally active agents to

humans and wildlife is difficult because exposure to these agents has

not been routinely monitored . . . . Background concentrations of

hormonally active agents in humans, particularly in adipose (fat) tissue

and blood, and other biota need to be established. In particular, routes

of exposure and the effects of diet need to be assessed to provide a

framework for examining the effects of these compounds in the general

population and in highly-exposed subpopulations.”

History of Federal

Efforts to Collect

Human Exposure Data

Since 1967, HHS and EPA have conducted federal surveys to assess the U.S.

population’s exposures to toxic chemicals from the analysis of human

tissue samples. While their efforts measured some of the same exposures

and covered some of the same time periods, their goals differed and most

did not include a nationally representative sample of citizens. EPA’s efforts

first monitored exposure to pesticides and, more recently, have attempted

to link human exposure data to specific routes of exposure. CDC’s periodic

surveys are intended to monitor trends in the health and nutrition status of

the population but, over time, have included exposures to environmental

toxics as one component of the general survey. NIEHS’ Human Exposure

Initiative, established in the late 1990s, is intended to help the agency

prioritize chemicals for further toxicology and carcinogenicity testing.

Within these studies, various subgroups have been used to develop human

exposure estimates, but in most cases, sampling has not been for all

participant groups or random. Consequently, the results cannot be

projected to the U.S. population as a whole for most chemicals. See table 5

for the time frames and numbers of chemicals covered for major federal

efforts.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 55 GAO/HEHS-00-80 Environmental Health Data Needs

Table 5: Number of Chemicals and Time Frames for Select Federal Efforts

a

The number of participants in NHANES II and NHANES III who received physical examinations is

used as a proxy for the number providing biological samples, as the latter number was not readily

available.

b

The number of persons examined in a calendar year is planned to be about 5,000.

c

For NHANES, the list of potentially toxic chemicals covered was provided by CDC laboratory officials.

For NHEXAS, the list of potentially toxic chemicals covered was provided by EPA NHEXAS officials.

d

According to a CDC laboratory official, lead and cadmium are measured in all participants. Cotinine

will also be measured in many participants—specifically, those ages 4 and older.

e

Chemicals analyzed by NHATS varied over time. NHATS collected data on 20 pesticides between

1970 and 1981. NIEHS chemicals are not included because data were not available at the time of our

review.

f

Excludes a related but separate study done in Minnesota reviewing pesticide exposures that was not

one of the three formal pilot surveys.

A description of these federal efforts to collect human exposure data

follows.

• CDC’s National Health and Nutrition Examination Surveys: NHANES,

conducted multiple times since 1960 by NCHS, is designed to provide

national estimates of the health and nutrition status of the

noninstitutionalized civilian population of the United States. Estimates

are obtained by examining randomly selected participants in a manner

that accurately reflects the demographic characteristics of the U.S.

population. Participants are given comprehensive physical

examinations (including tissue samples) and are interviewed on issues

Duration

Number of

participants

providing

biological samples

Number of

chemicals measured

for any participants

Number of

chemicals

measured

for all participants

(ages 1 and older)

Second National Health and Nutrition Examination Survey (NHANES II)

1976-1980 20,000 examineda 36 1

Third National Health and Nutrition Examination Survey (NHANES III)

1988-1994 30,000 examineda 47 1

National Health and Nutrition Examination Survey, 1999 (NHANES)

1999-ongoing 5,000 per yearb 74c 2d

National Human Adipose Tissue Survey (NHATS)

1967-1992 14,000 128 20e

National Human Exposure Assessment Survey (NHEXAS) Pilot Study

1995-1999 460f 46c 6
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 56 GAO/HEHS-00-80 Environmental Health Data Needs

such as their nutritional habits, health conditions, and housing

characteristics. NHANES data are used for a number of purposes. For

example, in addition to monitoring changes in blood lead levels, uses of

NHANES include development of national standards for blood pressure

and cholesterol levels and for determining infection rates for diseases.

CDC’s laboratory housed at NCEH performs the measurements of

chemicals in human tissues for NHANES.

• Second National Health and Nutrition Examination Survey: NHANES II

was designed to provide national estimates of the health and nutritional

status of the civilian noninstitutionalized population of the United States

for persons aged 6 months to 74 years. Children, the elderly and people

classified as living at or below the poverty level were oversampled in

order to increase the reliability of the estimates for these groups.

Measurements of pesticide residues were taken from participants who

were between the ages of 12 and 74 years of age.3 Blood lead

measurements were taken from participants in all age groups in the

survey.

• Third National Health and Nutrition Examination Survey: NHANES III

was designed to provide national estimates of health and nutritional

status of the civilian noninstitutionalized population of the United States

ages 2 months and older. Children ages 2 months through 5 years,

blacks, Mexican-Americans, and persons ages 60 or older were

oversampled to increase the reliability of the estimates for these groups.

Blood lead measurements were taken from all participants ages 1 year

or older. Cadmium measurements were taken from all participants ages

6 years or older. In addition, some participants ages 20 through 59 years

had measurements taken for volatile organic compounds and pesticides.

Participants volunteered for these additional measurements, so the

results cannot be projected to the population as a whole. However, the

results still serve as the reference ranges for these chemicals.

• National Health and Nutrition Examination Survey, 1999: In 1999, NCHS

changed the design of NHANES so that it will now be conducted as a

continuous survey of about 5,000 participants annually. Like the

previous surveys, NHANES will yield nationally representative results

for the civilian noninstitutionalized population. The NHANES design

will allow for oversampling to vary between years; persons aged 12 to

19, persons aged 60 and over, blacks, and Mexican-Americans are being

oversampled. It will be tied to related federal government data

3

Data were not publicly available, as CDC is resolving some methodological issues

associated with data collection.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 57 GAO/HEHS-00-80 Environmental Health Data Needs

collections conducted on the general U.S. population, in particular, the

National Health Interview Survey.4 NCHS also plans to release results

from the survey every year after the first 3 years of data collection. More

than 1 year of data will be required for many estimates, particularly

among detailed subgroups of the population. While lead and cadmium

will be the only potentially toxic chemicals measured for all participants

ages 1 and older (although cotinine, a metabolite which illustrates

exposure to environmental tobacco smoke, will be measured for most

age groups—those ages 4 and over), NCHS and NCEH plan to get

nationally representative data for specific chemicals for persons in

specific demographic groups, such as mercury measurements in women

ages 16 through 49. NCHS will also measure household lead dust,

drinking water contaminants, and exposure to volatile organic

compounds for selected participants. In addition to conducting an

annual national survey, NCHS is developing a smaller, more targeted

health survey—the Defined Population Health and Nutrition

Examination Survey (DP-HANES). NCHS recognizes that NHANES

cannot collect information that would be directly useful at the local or

state level or for small populations. DP-HANES is intended to address

this issue through the use of small mobile examination centers that

would visit areas of interest and examine 2,000 to 3,000 participants for

each special study. DP-HANES participants would not receive the full

range of tests given under NHANES; rather, the DP-HANES examination

would be tailored to the specific needs of the population under study.

• EPA’s National Human Adipose Tissue Survey: NHATS was intended to

be a continuously operating survey that would collect, store, and

analyze samples of autopsy and surgical specimens of human adipose

tissue from major metropolitan areas of the country. It was established

by HHS in 1967 and was transferred to EPA in 1970. During its existence,

NHATS data documented the widespread and significant prevalence of

pesticide exposures in the general population. NHATS data also showed

that reduced use of polychlorinated biphenyls (PCB) and DDT and

dieldrin (common insecticides) resulted in lower tissue concentrations

of these compounds. A trend analysis for 1970 through 1981 of NHATS

data showed a dramatic decline in PCB concentrations after the

regulation of PCBs in 1976. During the 1980s, problems with NHATS’

survey design, management, and goals were compounded by insufficient

financial support and caused the usefulness and quality of NHATS to

4

The sampling will be conducted on different people, but some questions asked in each

survey will be the same.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 58 GAO/HEHS-00-80 Environmental Health Data Needs

deteriorate. In 1991, NRC conducted a study to review and evaluate the

effectiveness and potential applications of NHATS.5 The study

concluded that a more comprehensive national program of human

tissue monitoring was a critical need for understanding human

exposures to environmental toxics. In addition, EPA needed a human

tissue monitoring program in order to evaluate the need and

effectiveness of EPA’s regulatory programs. The study recommended

that NHATS be completely redesigned to provide more useful data based

on probability samples of the whole U.S. population and that funding be

increased to permit the program to fulfill its mission. EPA ended the

NHATS in 1992 and replaced it with the NHEXAS pilot surveys.

• EPA’s National Human Exposure Assessment Survey Pilot Surveys: The

NHEXAS pilot surveys were designed to obtain knowledge on the

multiple pathways and media population distribution of exposures to

several classes of chemicals and to test the feasibility of conducting a

national survey to provide estimates on the status of human exposure to

potentially high-risk chemicals. NHEXAS was also designed to measure

“total exposure”—the levels of chemicals participants take in through

the air they breathe; the food, drinking water, and other beverages they

consume; and in the soil and dust around their homes. Measurements

have also been made of chemicals in biological samples (such as blood

and urine) provided by some participants. Participants completed

questionnaires to help identify possible sources of exposure to

chemicals. As designed, NHEXAS has three phases. Phase I is intended

to develop and validate NHEXAS methods, phase II is designed to obtain

nationally representative exposure data in a manner similar to that used

by NHANES to get health data, and phase III is designed to follow up on

information developed from phase II and will study selected

subpopulations. EPA conducted NHEXAS phase I (pilot) surveys in

Arizona, Maryland, and EPA’s region 5 (Illinois, Indiana, Michigan,

Minnesota, Ohio, and Wisconsin). About 460 participants in the pilot

surveys provided biological samples; examinations measured a variety

of chemicals, such as volatile organic compounds, heavy metals, and

pesticides. Human tissue measurements were performed under

interagency agreement by CDC’s environmental health laboratory. EPA

has completed most of the fieldwork for the NHEXAS phase I surveys

and is now analyzing the results. Based on these results, EPA will

finalize the scope and methods for NHEXAS phases II and III.

5

NRC, Commission on Life Sciences, Monitoring Human Tissues for Toxic Substances.
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 59 GAO/HEHS-00-80 Environmental Health Data Needs

• ATSDR’s Exposure Investigations: As part of its health assessment

process or in response to requests, ATSDR may conduct limited

biological monitoring at hazardous waste sites or other locations

through a process called exposure investigations. In response to the

recognition that the conclusions drawn from indirect methods of

measuring exposures were often not accurate and not reliable for

assessing potential health impacts and the need for more direct

measures of exposures, ATSDR formally established an exposure

investigation unit within its Division of Health Assessments and

Consultation. The Exposure Investigation Section was established in

1995 and is comprised of nine staff members who respond to requests to

conduct exposure investigations around hazardous waste sites. These

investigations involve gathering biological samples, conducting personal

monitoring for site-related contaminants and their byproducts, and

analyzing environmental data using computational tools.

In 1996, ATSDR convened an expert review panel to comment on

ATSDR’s exposure investigation program, including whether ATSDR

was on the right track in providing exposure information to improve

public health decisionmaking intended to address environmental

releases from hazardous waste sites. The panelists endorsed many

aspects of ATSDR’s investigative process, including the following:

• Conducting exposure investigations prior to preparing public health

assessments, which makes agency responsibilities easier because

information is provided that enables federal agencies to take action and

respond to community concerns in a timely manner.

• Considering exposure determinations to be as important as obtaining

environmental monitoring results.

• Emphasizing the human element of exposure investigations, which

illustrates that the federal government responds to community

concerns.

The panel also made several suggested improvements to the process,

including establishing a national clearinghouse of exposure

investigation data and results and developing site criteria and a protocol

for identifying who will decide on sites to target for exposure

investigation.

ATSDR’s exposure investigations have been valuable but limited in

scope. ATSDR used biological monitoring in conducting 47 exposure

investigations between 1995 and July 1999. Of these investigations, 17
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 60 GAO/HEHS-00-80 Environmental Health Data Needs

were done in support of the 460 health assessments done at that time.

Unlike NHANES and the NHEXAS pilot surveys, exposure investigations

usually have a small number of participants (less than 100) who

volunteer to participate in the study. While the exposure investigations

are not intended to be used for generalizations about larger populations,

the studies have proven very useful in ATSDR’s community outreach and

intervention activities.

• NIEHS’ Human Exposure Initiative: In 1996, this initiative, a

collaboration between NIEHS and CDC, was started to improve

understanding of human exposures to hormonally active agents—also

called “environmental endocrine disrupters”—for the national

population. CDC’s environmental health laboratory under an

interagency agreement is developing methods for and measuring up to

80 chemicals thought to be hormonally active agents in blood, urine, or

both. Human tissue samples used for these measurements are largely

obtained from the ongoing sampling of the general population under

NHANES and total about 200 in number.

In 1999, NIEHS and NTP officials proposed to expand the initial

collaboration between NIEHS and CDC by quantifying human internal

exposures to selected chemicals that are released into the environment

and workplace. NTP officials indicated this information would benefit

public health and priority-setting in a number of ways. First, it would

strengthen the scientific foundation for risk assessments by allowing (1)

the development of more credible relationships between exposure and

response in people thereby improving cross-species extrapolation, (2)

the development of biologically based dose-response models, and (3)

the identification of sensitive subpopulations and for estimates of risk

based on “margin of exposure.” Second, it would provide the kind of

information necessary for deciding which chemicals should be studied

with the limited resources available for toxicological testing. For

example, there are 85,000 chemicals in commerce today, and NTP can

provide toxicological evaluations on 10 to 20 per year. Third, the

information could be used to identify and help focus research on those

mixtures of chemicals that are actually present in people’s bodies.

Fourth, the types and amount of chemicals in children and other

potentially sensitive subpopulations would be identified.

Determinations of whether additional safety factors need to be applied

to children must rest in part upon comparative exposure analyses

between children and adults. Fifth, this initiative, taken together with

the environmental genome initiative, will provide the science base
Appendix II

Reported Gaps in Human Exposure Data and

History of Federal Efforts

Page 61 GAO/HEHS-00-80 Environmental Health Data Needs

essential for meaningful studies on gene and environment interactions,

particularly for strengthening the evaluation of epidemiology studies.

Finally, efficacy of public health policies aimed at reducing human

exposure to chemical agents could be evaluated in a more meaningful

way if human exposure data were available over time, including

remediation around Superfund sites and efforts to achieve

environmental equity.
Page 62 GAO/HEHS-00-80 Environmental Health Data Needs

Appendix III

Survey of State Environmental Health

Officials and Results ApendxiI
Appendix III

Survey of State Environmental Health

Officials and Results

Page 63 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix III

Survey of State Environmental Health

Officials and Results

Page 64 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix III

Survey of State Environmental Health

Officials and Results

Page 65 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix III

Survey of State Environmental Health

Officials and Results

Page 66 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix III

Survey of State Environmental Health

Officials and Results

Page 67 GAO/HEHS-00-80 Environmental Health Data Needs
Page 68 GAO/HEHS-00-80 Environmental Health Data Needs

Appendix IV

Comments From the Department of Health

and Human Services ApendxiIV
Appendix IV

Comments From the Department of Health

and Human Services

Page 69 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix IV

Comments From the Department of Health

and Human Services

Page 70 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix IV

Comments From the Department of Health

and Human Services

Page 71 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix IV

Comments From the Department of Health

and Human Services

Page 72 GAO/HEHS-00-80 Environmental Health Data Needs
Page 73 GAO/HEHS-00-80 Environmental Health Data Needs

Appendix V

Comments From the Environmental

Protection Agency ApendxiV

Now on page 6.

Now on page 41.
Appendix V

Comments From the Environmental

Protection Agency

Page 74 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix V

Comments From the Environmental

Protection Agency

Page 75 GAO/HEHS-00-80 Environmental Health Data Needs
Appendix V

Comments From the Environmental

Protection Agency

Page 76 GAO/HEHS-00-80 Environmental Health Data Needs

Now on page 5.

Now on page 7.

Now on page 31.

See page 26.
Appendix V

Comments From the Environmental

Protection Agency

Page 77 GAO/HEHS-00-80 Environmental Health Data Needs
Page 78 GAO/HEHS-00-80 Environmental Health Data Needs

Appendix VI

Major Contributors to This Report ApendxiVI

GAO Contact Katherine Iritani, Evaluator-in-Charge, (206) 287-4820

Staff

Acknowledgments

The following individuals made important contributions to this report:

Frank Pasquier served as Assistant Director; Cheryl Williams, Senior

Evaluator, performed the literature review, assessed barriers, performed

state site visits, and—along with Anita Kay, Intern—administered the

survey of state environmental health officials; Tim Clouse, Evaluator

assessed federal efforts and evaluated information collected for identifying

at-risk populations; Sharon Silas, Intern, and Evan Stoll, Technical Analyst,

compiled and analyzed the lists of toxic chemicals; Sylvia Shanks served as

attorney-adviser, and Stan Stenersen guided the message development and

report writing.

(108398) Letr
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